2014 AMC 10A Problem 11

Attempt Problem 11 of the 2014 AMC 10A below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2014 AMC 10A solutions, or check the answer key.

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11.

A customer who intends to purchase an appliance has three coupons, only one of which may be used:

Coupon 1:1: 10%10\% off the listed price if the listed price is at least $50\$50

Coupon 2:2: $20\$ 20 off the listed price if the listed price is at least $100\$100

Coupon 3:3: 18%18\% off the amount by which the listed price exceeds $100\$100

For which of the following listed prices will coupon 11 offer a greater price reduction than either coupon 22 or coupon 3?3?

$179.95\$ 179.95

$199.95\$ 199.95

$219.95\$ 219.95

$239.95\$ 239.95

$259.95\$ 259.95

Answer: C
Concepts:inequalitypercentage
Difficulty rating: 1540
Solution:

Let us analyze what these coupons do to an arbitrary price, x.x.

Coupon 11 changes this price to .9x..9x. Coupon 22 changes the price to x20.x - 20. Coupon 33 changes the price to x.18(x100)=.82x+18. x - .18(x - 100) = .82x + 18.

We want .9x<x20 .9x \lt x - 20 and .9x<.82x+18. .9x \lt .82x + 18. Solving both gives us 200<x<225.200 \lt x \lt 225.

The only answer choice that works is $219.95.\$ 219.95.

Thus, C is the correct answer.

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