Bunuel wrote:

What is the sum of all integers from 45 to 155 inclusive?

A. 10,000

B. 10,100

C. 11,000

D. 11,100

E. 13,200

A quick way to perform this arithmetic is to recall that if we know the average of a set of numbers, we can multiply by the number of numbers (i.e., the quantity) to get the sum. We can use the equation: sum = average x quantity

average of evenly-spaced set = (smallest number + largest number)/2 = (45 + 155)/2 = 200/2 = 100

quantity = 155 - 45 + 1 = 111

Thus, the sum is 100 x 111 = 11,100

Answer: D

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