Problem Solving

A breakfast that consists of 1 ounce of
corn puffs and 8 ounces of fruit X
provides 257 calories. When 8 ounces
of fruit Y is substituted for the 8
ounces of fruit X, the total number of
calories is reduced to 185. If fruit X
provides 1.8 times as many calories as
fruit Y, how many calories does 8
ounces of fruit Y alone provide ?
(A) 11.25
(B) 72
(C) 90
(D) 95
(E) 129.6

OA is C

Assume that each ounce of corn puffs provides c calories and each ounce of fruit x provides x calories.

c + 8x = 257

After the substitution, we find that that number of calories that fruit y provides for each ounce is x/(1.8).

c + 8x/(1.8) = 185

Solving both the equations:

8x(8/18) = 72 => x = 81/4 calories

8 ounces of fruit y provides 8(81/4)(10/18) = 20/18 * 81 = 90 calories

Choose C.