How much did he pay for each pie and cake?

Question

A boy bought 3 cakes and 4 pies from a shop and received $7.50 change from $40. If he had bought 4 cakes and 3 pies from the same shop, then he would have received $0.75 change instead. How much did he pay for each cake and each pie?

Answer 1

Carin,

What he paid 1st time = 40 - 7.5 = $32.50

What he would have paid in the 2nd case = 40 - 0.75 = $39.25

 

x = unit price of cake

y = unit price of pie

 

3x + 4y = 32.50 ----------------- y = (32.5 -3x)/4

4x + 3y = 39.25

 

4x + 3((32.5 -3x)/4) = 39.25

 

Can you finish this?