{"id":90426,"date":"2025-06-01T10:28:23","date_gmt":"2025-06-01T10:28:23","guid":{"rendered":"https:\/\/exam.pscnotes.com\/mcq\/?p=90426"},"modified":"2025-06-01T10:28:23","modified_gmt":"2025-06-01T10:28:23","slug":"when-the-digits-of-two-digit-numbers-are-reversed-the-number-increase","status":"publish","type":"post","link":"https:\/\/exam.pscnotes.com\/mcq\/when-the-digits-of-two-digit-numbers-are-reversed-the-number-increase\/","title":{"rendered":"When the digits of two-digit numbers are reversed, the number increase"},"content":{"rendered":"<p>When the digits of two-digit numbers are reversed, the number increases by 27, the sum of such two-digit numbers is<\/p>\n<p>[amp_mcq option1=&#8221;235&#8243; option2=&#8221;249&#8243; option3=&#8221;213&#8243; option4=&#8221;180&#8243; correct=&#8221;option2&#8243;]<\/p>\n<div class=\"psc-box-pyq-exam-year-detail\">\n<div class=\"pyq-exam\">\n<div class=\"psc-heading\">This question was previously asked in<\/div>\n<div class=\"psc-title line-ellipsis\">UPSC CAPF &#8211; 2019<\/div>\n<\/div>\n<div class=\"pyq-exam-psc-buttons\"><a href=\"\/pyq\/pyq-upsc-capf-2019.pdf\" target=\"_blank\" class=\"psc-pdf-button\" rel=\"noopener\">Download PDF<\/a><a href=\"\/pyq-upsc-capf-2019\" target=\"_blank\" class=\"psc-attempt-button\" rel=\"noopener\">Attempt Online<\/a><\/div>\n<\/div>\n<section id=\"pyq-correct-answer\">\nThe correct answer is B) 249.<br \/>\n<\/section>\n<section id=\"pyq-key-points\">\nLet the two-digit number be represented as 10t + u, where t is the tens digit (t \u2208 {1, 2, &#8230;, 9}) and u is the units digit (u \u2208 {0, 1, &#8230;, 9}).<br \/>\nWhen the digits are reversed, the new number is 10u + t.<br \/>\nThe problem states that the number increases by 27 when the digits are reversed.<br \/>\nSo, (10u + t) &#8211; (10t + u) = 27.<br \/>\n10u + t &#8211; 10t &#8211; u = 27<br \/>\n9u &#8211; 9t = 27<br \/>\n9(u &#8211; t) = 27<br \/>\nu &#8211; t = 3.<br \/>\nThis condition means the units digit is 3 greater than the tens digit. We need to find all two-digit numbers (10t + u) that satisfy this condition, keeping in mind the constraints on t and u.<br \/>\nPossible pairs (t, u) where u &#8211; t = 3:<br \/>\n&#8211; If t = 1, u = 1 + 3 = 4. The number is 14. Reversed: 41 (41 &#8211; 14 = 27). Valid.<br \/>\n&#8211; If t = 2, u = 2 + 3 = 5. The number is 25. Reversed: 52 (52 &#8211; 25 = 27). Valid.<br \/>\n&#8211; If t = 3, u = 3 + 3 = 6. The number is 36. Reversed: 63 (63 &#8211; 36 = 27). Valid.<br \/>\n&#8211; If t = 4, u = 4 + 3 = 7. The number is 47. Reversed: 74 (74 &#8211; 47 = 27). Valid.<br \/>\n&#8211; If t = 5, u = 5 + 3 = 8. The number is 58. Reversed: 85 (85 &#8211; 58 = 27). Valid.<br \/>\n&#8211; If t = 6, u = 6 + 3 = 9. The number is 69. Reversed: 96 (96 &#8211; 69 = 27). Valid.<br \/>\n&#8211; If t = 7, u = 7 + 3 = 10 (not a single digit). So, we stop here.<br \/>\nThe two-digit numbers that satisfy the condition are 14, 25, 36, 47, 58, and 69.<br \/>\nThe sum of these numbers is 14 + 25 + 36 + 47 + 58 + 69.<br \/>\nSum = (10+4) + (20+5) + (30+6) + (40+7) + (50+8) + (60+9)<br \/>\nSum = (10+20+30+40+50+60) + (4+5+6+7+8+9)<br \/>\nSum = 210 + 39 = 249.<br \/>\nAlternatively, Sum = (14 + 69) + (25 + 58) + (36 + 47) = 83 + 83 + 83 = 3 * 83 = 249.<br \/>\n<\/section>\n<section id=\"pyq-additional-information\">\nProblems involving two-digit numbers and reversed digits often lead to simple linear equations relating the tens and units digits, typically involving a multiple of 9.<br \/>\n<\/section>\n","protected":false},"excerpt":{"rendered":"<p>When the digits of two-digit numbers are reversed, the number increases by 27, the sum of such two-digit numbers is [amp_mcq option1=&#8221;235&#8243; option2=&#8221;249&#8243; option3=&#8221;213&#8243; option4=&#8221;180&#8243; correct=&#8221;option2&#8243;] This question was previously asked in UPSC CAPF &#8211; 2019 Download PDFAttempt Online The correct answer is B) 249. Let the two-digit number be represented as 10t + u, &#8230; <\/p>\n<p class=\"read-more-container\"><a title=\"When the digits of two-digit numbers are reversed, the number increase\" class=\"read-more button\" href=\"https:\/\/exam.pscnotes.com\/mcq\/when-the-digits-of-two-digit-numbers-are-reversed-the-number-increase\/#more-90426\">Detailed Solution<span class=\"screen-reader-text\">When the digits of two-digit numbers are reversed, the number increase<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1085],"tags":[1119,1102],"class_list":["post-90426","post","type-post","status-publish","format-standard","hentry","category-upsc-capf","tag-1119","tag-quantitative-aptitude-and-reasoning","no-featured-image-padding"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v22.2 (Yoast SEO v23.3) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>When the digits of two-digit numbers are reversed, the number increase<\/title>\n<meta name=\"description\" content=\"The correct answer is B) 249. Let the two-digit number be represented as 10t + u, where t is the tens digit (t \u2208 {1, 2, ..., 9}) and u is the units digit (u \u2208 {0, 1, ..., 9}). When the digits are reversed, the new number is 10u + t. The problem states that the number increases by 27 when the digits are reversed. So, (10u + t) - (10t + u) = 27. 10u + t - 10t - u = 27 9u - 9t = 27 9(u - t) = 27 u - t = 3. This condition means the units digit is 3 greater than the tens digit. We need to find all two-digit numbers (10t + u) that satisfy this condition, keeping in mind the constraints on t and u. Possible pairs (t, u) where u - t = 3: - If t = 1, u = 1 + 3 = 4. The number is 14. Reversed: 41 (41 - 14 = 27). Valid. - If t = 2, u = 2 + 3 = 5. The number is 25. Reversed: 52 (52 - 25 = 27). Valid. - If t = 3, u = 3 + 3 = 6. The number is 36. Reversed: 63 (63 - 36 = 27). Valid. - If t = 4, u = 4 + 3 = 7. The number is 47. Reversed: 74 (74 - 47 = 27). Valid. - If t = 5, u = 5 + 3 = 8. The number is 58. Reversed: 85 (85 - 58 = 27). Valid. - If t = 6, u = 6 + 3 = 9. The number is 69. Reversed: 96 (96 - 69 = 27). Valid. - If t = 7, u = 7 + 3 = 10 (not a single digit). So, we stop here. The two-digit numbers that satisfy the condition are 14, 25, 36, 47, 58, and 69. The sum of these numbers is 14 + 25 + 36 + 47 + 58 + 69. Sum = (10+4) + (20+5) + (30+6) + (40+7) + (50+8) + (60+9) Sum = (10+20+30+40+50+60) + (4+5+6+7+8+9) Sum = 210 + 39 = 249. Alternatively, Sum = (14 + 69) + (25 + 58) + (36 + 47) = 83 + 83 + 83 = 3 * 83 = 249.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/exam.pscnotes.com\/mcq\/when-the-digits-of-two-digit-numbers-are-reversed-the-number-increase\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"When the digits of two-digit numbers are reversed, the number increase\" \/>\n<meta property=\"og:description\" content=\"The correct answer is B) 249. Let the two-digit number be represented as 10t + u, where t is the tens digit (t \u2208 {1, 2, ..., 9}) and u is the units digit (u \u2208 {0, 1, ..., 9}). When the digits are reversed, the new number is 10u + t. The problem states that the number increases by 27 when the digits are reversed. So, (10u + t) - (10t + u) = 27. 10u + t - 10t - u = 27 9u - 9t = 27 9(u - t) = 27 u - t = 3. This condition means the units digit is 3 greater than the tens digit. We need to find all two-digit numbers (10t + u) that satisfy this condition, keeping in mind the constraints on t and u. Possible pairs (t, u) where u - t = 3: - If t = 1, u = 1 + 3 = 4. The number is 14. Reversed: 41 (41 - 14 = 27). Valid. - If t = 2, u = 2 + 3 = 5. The number is 25. Reversed: 52 (52 - 25 = 27). Valid. - If t = 3, u = 3 + 3 = 6. The number is 36. Reversed: 63 (63 - 36 = 27). Valid. - If t = 4, u = 4 + 3 = 7. The number is 47. Reversed: 74 (74 - 47 = 27). Valid. - If t = 5, u = 5 + 3 = 8. The number is 58. Reversed: 85 (85 - 58 = 27). Valid. - If t = 6, u = 6 + 3 = 9. The number is 69. Reversed: 96 (96 - 69 = 27). Valid. - If t = 7, u = 7 + 3 = 10 (not a single digit). So, we stop here. The two-digit numbers that satisfy the condition are 14, 25, 36, 47, 58, and 69. The sum of these numbers is 14 + 25 + 36 + 47 + 58 + 69. Sum = (10+4) + (20+5) + (30+6) + (40+7) + (50+8) + (60+9) Sum = (10+20+30+40+50+60) + (4+5+6+7+8+9) Sum = 210 + 39 = 249. Alternatively, Sum = (14 + 69) + (25 + 58) + (36 + 47) = 83 + 83 + 83 = 3 * 83 = 249.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/exam.pscnotes.com\/mcq\/when-the-digits-of-two-digit-numbers-are-reversed-the-number-increase\/\" \/>\n<meta property=\"og:site_name\" content=\"MCQ and Quiz for Exams\" \/>\n<meta property=\"article:published_time\" content=\"2025-06-01T10:28:23+00:00\" \/>\n<meta name=\"author\" content=\"rawan239\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"rawan239\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"1 minute\" \/>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"When the digits of two-digit numbers are reversed, the number increase","description":"The correct answer is B) 249. Let the two-digit number be represented as 10t + u, where t is the tens digit (t \u2208 {1, 2, ..., 9}) and u is the units digit (u \u2208 {0, 1, ..., 9}). When the digits are reversed, the new number is 10u + t. The problem states that the number increases by 27 when the digits are reversed. So, (10u + t) - (10t + u) = 27. 10u + t - 10t - u = 27 9u - 9t = 27 9(u - t) = 27 u - t = 3. This condition means the units digit is 3 greater than the tens digit. We need to find all two-digit numbers (10t + u) that satisfy this condition, keeping in mind the constraints on t and u. Possible pairs (t, u) where u - t = 3: - If t = 1, u = 1 + 3 = 4. The number is 14. Reversed: 41 (41 - 14 = 27). Valid. - If t = 2, u = 2 + 3 = 5. The number is 25. Reversed: 52 (52 - 25 = 27). Valid. - If t = 3, u = 3 + 3 = 6. The number is 36. Reversed: 63 (63 - 36 = 27). Valid. - If t = 4, u = 4 + 3 = 7. The number is 47. Reversed: 74 (74 - 47 = 27). Valid. - If t = 5, u = 5 + 3 = 8. The number is 58. Reversed: 85 (85 - 58 = 27). Valid. - If t = 6, u = 6 + 3 = 9. The number is 69. Reversed: 96 (96 - 69 = 27). Valid. - If t = 7, u = 7 + 3 = 10 (not a single digit). So, we stop here. The two-digit numbers that satisfy the condition are 14, 25, 36, 47, 58, and 69. The sum of these numbers is 14 + 25 + 36 + 47 + 58 + 69. Sum = (10+4) + (20+5) + (30+6) + (40+7) + (50+8) + (60+9) Sum = (10+20+30+40+50+60) + (4+5+6+7+8+9) Sum = 210 + 39 = 249. Alternatively, Sum = (14 + 69) + (25 + 58) + (36 + 47) = 83 + 83 + 83 = 3 * 83 = 249.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/exam.pscnotes.com\/mcq\/when-the-digits-of-two-digit-numbers-are-reversed-the-number-increase\/","og_locale":"en_US","og_type":"article","og_title":"When the digits of two-digit numbers are reversed, the number increase","og_description":"The correct answer is B) 249. Let the two-digit number be represented as 10t + u, where t is the tens digit (t \u2208 {1, 2, ..., 9}) and u is the units digit (u \u2208 {0, 1, ..., 9}). When the digits are reversed, the new number is 10u + t. The problem states that the number increases by 27 when the digits are reversed. So, (10u + t) - (10t + u) = 27. 10u + t - 10t - u = 27 9u - 9t = 27 9(u - t) = 27 u - t = 3. This condition means the units digit is 3 greater than the tens digit. We need to find all two-digit numbers (10t + u) that satisfy this condition, keeping in mind the constraints on t and u. Possible pairs (t, u) where u - t = 3: - If t = 1, u = 1 + 3 = 4. The number is 14. Reversed: 41 (41 - 14 = 27). Valid. - If t = 2, u = 2 + 3 = 5. The number is 25. Reversed: 52 (52 - 25 = 27). Valid. - If t = 3, u = 3 + 3 = 6. The number is 36. Reversed: 63 (63 - 36 = 27). Valid. - If t = 4, u = 4 + 3 = 7. The number is 47. Reversed: 74 (74 - 47 = 27). Valid. - If t = 5, u = 5 + 3 = 8. The number is 58. Reversed: 85 (85 - 58 = 27). Valid. - If t = 6, u = 6 + 3 = 9. The number is 69. Reversed: 96 (96 - 69 = 27). Valid. - If t = 7, u = 7 + 3 = 10 (not a single digit). So, we stop here. The two-digit numbers that satisfy the condition are 14, 25, 36, 47, 58, and 69. The sum of these numbers is 14 + 25 + 36 + 47 + 58 + 69. Sum = (10+4) + (20+5) + (30+6) + (40+7) + (50+8) + (60+9) Sum = (10+20+30+40+50+60) + (4+5+6+7+8+9) Sum = 210 + 39 = 249. Alternatively, Sum = (14 + 69) + (25 + 58) + (36 + 47) = 83 + 83 + 83 = 3 * 83 = 249.","og_url":"https:\/\/exam.pscnotes.com\/mcq\/when-the-digits-of-two-digit-numbers-are-reversed-the-number-increase\/","og_site_name":"MCQ and Quiz for Exams","article_published_time":"2025-06-01T10:28:23+00:00","author":"rawan239","twitter_card":"summary_large_image","twitter_misc":{"Written by":"rawan239","Est. reading time":"1 minute"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/exam.pscnotes.com\/mcq\/when-the-digits-of-two-digit-numbers-are-reversed-the-number-increase\/","url":"https:\/\/exam.pscnotes.com\/mcq\/when-the-digits-of-two-digit-numbers-are-reversed-the-number-increase\/","name":"When the digits of two-digit numbers are reversed, the number increase","isPartOf":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#website"},"datePublished":"2025-06-01T10:28:23+00:00","dateModified":"2025-06-01T10:28:23+00:00","author":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/5807dafeb27d2ec82344d6cbd6c3d209"},"description":"The correct answer is B) 249. Let the two-digit number be represented as 10t + u, where t is the tens digit (t \u2208 {1, 2, ..., 9}) and u is the units digit (u \u2208 {0, 1, ..., 9}). When the digits are reversed, the new number is 10u + t. The problem states that the number increases by 27 when the digits are reversed. So, (10u + t) - (10t + u) = 27. 10u + t - 10t - u = 27 9u - 9t = 27 9(u - t) = 27 u - t = 3. This condition means the units digit is 3 greater than the tens digit. We need to find all two-digit numbers (10t + u) that satisfy this condition, keeping in mind the constraints on t and u. Possible pairs (t, u) where u - t = 3: - If t = 1, u = 1 + 3 = 4. The number is 14. Reversed: 41 (41 - 14 = 27). Valid. - If t = 2, u = 2 + 3 = 5. The number is 25. Reversed: 52 (52 - 25 = 27). Valid. - If t = 3, u = 3 + 3 = 6. The number is 36. Reversed: 63 (63 - 36 = 27). Valid. - If t = 4, u = 4 + 3 = 7. The number is 47. Reversed: 74 (74 - 47 = 27). Valid. - If t = 5, u = 5 + 3 = 8. The number is 58. Reversed: 85 (85 - 58 = 27). Valid. - If t = 6, u = 6 + 3 = 9. The number is 69. Reversed: 96 (96 - 69 = 27). Valid. - If t = 7, u = 7 + 3 = 10 (not a single digit). So, we stop here. The two-digit numbers that satisfy the condition are 14, 25, 36, 47, 58, and 69. The sum of these numbers is 14 + 25 + 36 + 47 + 58 + 69. Sum = (10+4) + (20+5) + (30+6) + (40+7) + (50+8) + (60+9) Sum = (10+20+30+40+50+60) + (4+5+6+7+8+9) Sum = 210 + 39 = 249. Alternatively, Sum = (14 + 69) + (25 + 58) + (36 + 47) = 83 + 83 + 83 = 3 * 83 = 249.","breadcrumb":{"@id":"https:\/\/exam.pscnotes.com\/mcq\/when-the-digits-of-two-digit-numbers-are-reversed-the-number-increase\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/exam.pscnotes.com\/mcq\/when-the-digits-of-two-digit-numbers-are-reversed-the-number-increase\/"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/exam.pscnotes.com\/mcq\/when-the-digits-of-two-digit-numbers-are-reversed-the-number-increase\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/exam.pscnotes.com\/mcq\/"},{"@type":"ListItem","position":2,"name":"UPSC CAPF","item":"https:\/\/exam.pscnotes.com\/mcq\/category\/upsc-capf\/"},{"@type":"ListItem","position":3,"name":"When the digits of two-digit numbers are reversed, the number increase"}]},{"@type":"WebSite","@id":"https:\/\/exam.pscnotes.com\/mcq\/#website","url":"https:\/\/exam.pscnotes.com\/mcq\/","name":"MCQ and Quiz for Exams","description":"","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/exam.pscnotes.com\/mcq\/?s={search_term_string}"},"query-input":"required name=search_term_string"}],"inLanguage":"en-US"},{"@type":"Person","@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/5807dafeb27d2ec82344d6cbd6c3d209","name":"rawan239","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/exam.pscnotes.com\/mcq\/#\/schema\/person\/image\/","url":"https:\/\/secure.gravatar.com\/avatar\/761a7274f9cce048fa5b921221e7934820d74514df93ef195a9d22af0c1c9001?s=96&d=mm&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/761a7274f9cce048fa5b921221e7934820d74514df93ef195a9d22af0c1c9001?s=96&d=mm&r=g","caption":"rawan239"},"sameAs":["https:\/\/exam.pscnotes.com"],"url":"https:\/\/exam.pscnotes.com\/mcq\/author\/rawan239\/"}]}},"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts\/90426","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/comments?post=90426"}],"version-history":[{"count":0,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/posts\/90426\/revisions"}],"wp:attachment":[{"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/media?parent=90426"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/categories?post=90426"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/exam.pscnotes.com\/mcq\/wp-json\/wp\/v2\/tags?post=90426"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}