A triangle is formed with vertices (0, 0), (0, 100) and (100, 100). What is the number of points inside the triangle with integer coordinates?
The lines forming the boundaries of the triangle are:
1. The line segment AB is along the y-axis, from y=0 to y=100 (x=0).
2. The line segment BC is along the line y=100, from x=0 to x=100.
3. The line segment AC connects (0, 0) and (100, 100). The equation of this line is y = x.
A point (x, y) is strictly inside this triangle if it satisfies the following conditions:
1. It must be to the right of the line x=0: x > 0.
2. It must be below the line y=100: y < 100.
3. It must be above the line y=x: y > x.
Combining these, we are looking for integer coordinates (x, y) such that 0 < x < y < 100. Let's iterate through possible integer values for x. Since x > 0 and x < y < 100, the smallest possible integer value for x is 1. If x = 1, y must be an integer such that 1 < y < 100. Possible y values are 2, 3, ..., 99. The number of such y values is 99 - 2 + 1 = 98. If x = 2, y must be an integer such that 2 < y < 100. Possible y values are 3, 4, ..., 99. The number of such y values is 99 - 3 + 1 = 97. If x = 3, y must be an integer such that 3 < y < 100. Possible y values are 4, 5, ..., 99. The number of such y values is 99 - 4 + 1 = 96. ... What is the largest possible integer value for x? Since x < y < 100, the largest possible integer value for y is 99. This requires x to be at least 1 less than 99, i.e., x < 99. So, the largest possible integer value for x is 98. If x = 98, y must be an integer such that 98 < y < 100. The only possible y value is 99. The number of such y values is 1. (99 - 99 + 1 = 1) The total number of integer points inside the triangle is the sum of the number of possible y values for each x from 1 to 98. Total points = (99 - 1) + (99 - 2) + (99 - 3) + ... + (99 - 98) Total points = 98 + 97 + 96 + ... + 1 This is the sum of the first 98 positive integers. The formula for the sum of the first n positive integers is n(n+1)/2. Here, n = 98. Sum = 98 * (98 + 1) / 2 = 98 * 99 / 2 = 49 * 99. 49 * 99 = 49 * (100 - 1) = 4900 - 49 = 4851. The number of points inside the triangle with integer coordinates is 4851.