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Percentages Smart Math

[Smart Math] Percentages Problem 15

Here’s and example of a SMART MATH problem for PERCENTAGES.

Percentages

Problem

A man bought a watch marked at $400. He was given successive discount of 15% and 10%. What did he pay for the watch?

  1. $350
  2. $340
  3. $316
  4. $306
  5. $300

The Usual Method

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After applying 15% discount the price of the clock is $400 x 0.85 = 340

After applying 10% discount the price of the clock is $340 x 0.90 = 306

(Ans: 4)

Estimated Time to arrive at the answer = 30 seconds.

Using Technique

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A discount of 10% means 90% of the price or 0.9 times the price. The answer can be found by solving the expression 400 x 0.85 x 0.90. The answer should be a multiple of 9 due to the multiplication of 0.90. The only answer that is a multiple of 9 from amongst the options is $306 i.e. option ‘4’.

(Ans: 4)

Estimated Time to arrive at the answer = 10 seconds.
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