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Algebra Smart Math

[Smart Math] Algebra Problem 7

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

Algebra

Problem

20 years ago my age was 1/3rd of my present age. What is my present age now?

  1. 66 years
  2. 36 years
  3. 33 years
  4. 30 years
  5. None of these

The Usual Method

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Let the present age be ‘x’ years.

Hence, 20 years ago the age was (x – 20) years. Also this age is 1/3rd of the present age.

Hence, x-20=\frac{1}{3}x

\therefore 3x-60=x

\therefore 2x=60

\therefore x=30years

(Ans: 4)

Estimated Time to arrive at the answer = 30 seconds.

Using Technique

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Note that if, the age 20 years ago was 1/3rd of the present age, than 20 years represents 2/3rd of the present age. Hence, present age = 30 years.

(Ans: 4)

Estimated Time to arrive at the answer = 5 seconds.
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