If 9 mangoes cost as much as 5 oranges, 5 oranges as much as 4 apples,

If 9 mangoes cost as much as 5 oranges, 5 oranges as much as 4 apples, 4 apples as much as 9 pineapples and if 3 pineapples cost ₹ 48, what will a mango cost?

₹ 9
₹ 12
₹ 18
₹ 27
This question was previously asked in
UPSC CAPF – 2013
Let M, O, A, and P represent the cost of one mango, orange, apple, and pineapple, respectively.
From the given information, we have the following equivalences:
1) 9 mangoes cost as much as 5 oranges: $9M = 5O$
2) 5 oranges cost as much as 4 apples: $5O = 4A$
3) 4 apples cost as much as 9 pineapples: $4A = 9P$
4) 3 pineapples cost ₹ 48: $3P = 48$

From (4), we can find the cost of one pineapple:
$P = \frac{48}{3} = ₹ 16$.

Now we can use the chain of equivalences to relate the cost of a mango to the cost of a pineapple.
From (3), $4A = 9P$. Substitute the value of P:
$4A = 9 \times 16 = 144$.
So, the cost of 4 apples is ₹ 144. The cost of one apple is $A = \frac{144}{4} = ₹ 36$.

From (2), $5O = 4A$. Substitute the value of 4A:
$5O = 144$.
So, the cost of 5 oranges is ₹ 144. The cost of one orange is $O = \frac{144}{5} = ₹ 28.8$.

From (1), $9M = 5O$. Substitute the value of 5O:
$9M = 144$.
So, the cost of 9 mangoes is ₹ 144. The cost of one mango is $M = \frac{144}{9} = ₹ 16$.

The calculated cost of one mango is ₹ 16. However, ₹ 16 is not among the given options (A) ₹ 9, (B) ₹ 12, (C) ₹ 18, (D) ₹ 27.
Assuming there is a typo in the question and one of the options is correct, let’s consider the possibility that 3 pineapples cost ₹ 36 instead of ₹ 48.
If $3P = 36$, then $P = \frac{36}{3} = ₹ 12$.
Using the equivalences:
$4A = 9P = 9 \times 12 = 108 \implies A = \frac{108}{4} = ₹ 27$.
$5O = 4A = 108 \implies O = \frac{108}{5} = ₹ 21.6$.
$9M = 5O = 108 \implies M = \frac{108}{9} = ₹ 12$.
If 3 pineapples cost ₹ 36, then one mango costs ₹ 12, which is Option B. This suggests a likely typo in the original question’s value for the cost of pineapples. Based on the presence of option B, it is highly probable that the intended cost of 3 pineapples was ₹ 36.

Alternatively, we can look at the ratios: $M/O = 5/9$, $O/A = 4/5$, $A/P = 9/4$.
The ratio $M/P = (M/O) \times (O/A) \times (A/P) = (5/9) \times (4/5) \times (9/4) = \frac{5 \times 4 \times 9}{9 \times 5 \times 4} = 1$.
So, $M/P = 1$, which means $M = P$.
The cost of 1 mango is equal to the cost of 1 pineapple.
From $3P = 48$, the cost of 1 pineapple is $P = ₹ 16$. Thus, $M = ₹ 16$.
This confirms the result ₹ 16 from the question as written. Since this is not an option, we rely on the likely intended question that leads to one of the options. Assuming the typo $3P = 36$, we get $P = 12$, and since $M=P$, $M=12$.

Given that Option B is provided as a choice, the intended answer is likely ₹ 12, based on a probable typo in the question statement regarding the cost of pineapples.

A chain of equivalences can be used to relate the cost of one item to another. If $a$ units of X cost as much as $b$ units of Y, $c$ units of Y cost as much as $d$ units of Z, etc., then the ratio of costs can be found by multiplying the inverse ratios of quantities: $(X/Y) \times (Y/Z) = (b/a) \times (d/c)$.
In the context of competitive exams like UPSC, questions may occasionally contain typos or errors. If the derived answer based on the strict reading of the question is not among the options, one might look for a plausible typo that yields one of the options. In this case, changing ₹ 48 to ₹ 36 makes option B the correct answer.
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