mail a package

[GmatKiss]

To mail a package, the rate is x cents for the first
pound and y cents for each additional pound, where
x > y. Two packages weighing 3 pounds and 5 pounds,
respectively, can be mailed separately or combined as
one package. Which method is cheaper, and how
much money is saved?

(A) Combined, with a savings of x - y cents
(B) Combined, with a savings of y - x cents
(C) Combined, with a savings of x cents
(D) Separately, with a savings of x - y cents
(E) Separately, with a savings of y cents

[shankar.ashwin]

Assume x=5; y=3

Packing separately;

3 pounds - 5 + 6 = 11
5 pounds - 5 + 12 = 17

Total = 11+17=28

Together;

8 pounds - 5 + 21 = 26

Packing it combined is cheaper, with savings of 28-26=2 which is (x-y) A IMO

[ripulgupta]

Assume both package weigh A and B pounds.

If mailed separately it would cost x + (A -1)y for first package and x + (B-1) y for second package. Total cost is 2x + ( A + B - 2) y ---- Eq1

If mailed together it would cost x + (A + B -1 ) y --- Eq2

Difference in cost Eq1 - Eq2 = x - y. As x > y money is being saved.