The user-friendly version of this content is available here.
The following content is copyright (c) 2009-2013 by Goods of the Mind, LLC.
This problem trains for: SAT-I, AMC-8, GMAT.
The average of three integer numbers is divisible by 5. Which of the following values cannot be the sum of the numbers?
The average a of three integers x, y, z is given by:
If the average is divisible by 5 then it must be integer and be a multiple of 5:
where k is an integer.Therefore,
the sum of the numbers must be a multiple of 15. The only choice that is not divisible by 15 is 145.