John and Jane went out for a dinner and they ordered the

Hi All,

Since this question asks for the original price of the dish, and the answers are numbers, we can TEST THE ANSWERS.

We're told how two people pay their tips:

1) John paid a 15% tip on the original cost of the dish (which I'll call X dollars)
2) Jane paid a 15% tip on on the discounted price of the dish (which I'll call .9X dollars)
3) The difference in the tips was $0.63

When TESTing THE ANSWERS, it's usually best to start with either Answer B or Answer D. In this question, Answer D will be easier to deal with, so let's start there....

IF....the original cost of the dish = $42

15% tip on $42 = (.15)(42) = $6.30

From here, the "math" can be done in a couple of different ways. I've included the full calculation below, but since John's tip = $6.30, and Jane's tip is 10% less (since she paid her tip on the discounted dish which was 10% off), then the 10% of $6.30 is $0.63, which is exactly what we're looking for.

15% tip on (90% of $42) = (.15)($37.80) = $5.67

$6.30 - $5.67 = $0.63 This is a MATCH for what we were told, so D MUST be the answer.

Final Answer:

GMAT assassins aren't born, they're made,
Rich

Here's how I did.

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We can create the equation:

0.15x + 0.9x = 1.15(0.9x) + 0.63

1.05x = 1.035x + 0.63

0.015x = 0.63

x = 42

Answer: D

John and Jane went out for a dinner and they ordered the same dish. Both used a 10% discount coupon. John paid a 15% tip over the original price of the dish, while Jane paid the tip over the discounted price for the coupon. If John paid $0.63 more than Jane, what was the original price of the dish?

(A) 24
(B) 34.8
(C) 37.8
(D) 42
(E) 84

I used the multiplier concept
As the price of the dish is the same in both cases. Let price = $100
For John: Pays the tip over the original price of the dish then uses the coupon over that amount. = $100 + $15 - $10 = $105
For Jane: Pays the tip over the discounted price of the dish and uses the coupon over the reduced price = $100 - $10 + 13.5 = $103.5
Difference in bill amount when dish price = 100 is $1.5 if the difference is $0.63?
Price of the dish = \(63/150\)*100 = 42
\(D\)

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