Question

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. $100B. $150C. $200D. $250E. $450

Answer 1

`Z= 75*6 -250=200`

So then the correct answer is B. $200.

Explanation:

Notation

Let X be the average contribution size before John makes his contribution.

Let Y be the total contribution size before John makes his contribution.

Let Z be John's contribution.

We know that for this case $ 75 represent the original average amount before the contribution with 50% increase so we can set up the following equation in order to find the original average amount

`1.5 X = 75`

And solvong for X we got:

`X = (75)/(1.5)= 50`

Now we can find the total contribution before the donation with the following proportion:

`(50)/(1)= (Y)/(5)`

`Y = 250`

And then with the formula of average taking in count the 6 values we can find the size of donation Z like this:

`(Y+Z)/(6)= 75`

`(250+Z)/(6)= 75`

`Z= 75*6 -250=200`

So then the correct answer is B. $200.