Yesterday, Manhattan GMAT posted a 700 level GMAT question on our blog. Today, they have followed up with the answer:
Answer: E
Explanation:
In order to find the sum of consecutive numbers, we always follow three steps:
1. Find the number of numbers
2. Find the middle number
3. Multiply
1. Find the number of numbers:
The multiples of five between 23 and 92 are really the numbers starting from 25 and ending with 90. To find the number of numbers, subtract 25 from 90, divide by 5, and add 1:
90 – 25 = 65
65/5 = 13
13 + 1 = 14
2. Find the middle number:
The middle number between 25 and 90 is the average of 25 and 90:
25 + 90 = 115
115/2 = 57.5
3. Multiply:
57.5*14 = 805