[Smart Math] ALGEBRA PROBLEM 7

September 8, 2010 |

Author LazyMaths.com

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

Algebra

Problem

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

66 years
36 years
33 years
30 years
None of these

The Usual Method

Let the present age be ‘x’ years.

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

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

$\therefore 3x-60=x$ $\therefore 2x=60$

$\therefore x=30$ years

(Ans: 4)

Estimated Time to arrive at the answer = 30 seconds.

Using Technique

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

(Ans: 4)

Estimated Time to arrive at the answer = 5 seconds.

Rating: 8.0/10 (1 vote cast)

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