BTGmoderatorDC wrote:If john makes a contribution to a charity fund at school, the average contribution size will increase by 50% reaching $75 per person. If there were 5 other contributions made before john's, what is the size of his donation?
A. $100
B. $150
C. $200
D. $250
E. $450
Mitch's approach is the most straightforward. However, here's an algebraic version:
Let J = the John's donation
Let a, b, c, d and e = the donations of the other 5 donors.
John makes a contribution to a charity fund at school, the average contribution size will increase by 50% reaching $75 per person.
If the average contribution for all 6 donors = $75, we can write: (a + b + c + d + e + J)/6 = $75
Multiply both sides by 6 to get:
a + b + c + d + e + J = $450
John makes a contribution to a charity fund at school, the average contribution size will increase by 50% reaching $75 per person.
If we let x = the OLD (before John) average donation, then we can write 1.5x = $75
Solve for x to get x = $50
So, $50 is the OLD (before John) average donation for donors a, b, c, d and e
We can write: (a + b + c + d + e)/5 = $50
Multiply both sides by 5 to get:
a + b + c + d + e = $250
We now have two equations:
a + b + c + d + e + J = $450
a + b + c + d + e = $250
Subtract the bottom equation from the top equation to get: J = $200
Answer: C
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
