Here’s and example of a SMART MATH problem for ALGEBRA.
Problem
Tom is 6 years elder to Dick. 20 years ago, Tom was 15 times older than Harry, but now Dick is twice as old as Harry. What is the age of Dick?
- 44
- 48
- 50
- 52
- 54
The Usual Method
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Let the present age of Dick be ‘x’ years.
Hence, age of Harry = years.
Age of Harry 20 years ago =
Present age of Tom =
Age of Tom 20 years ago =
years
(Ans: 1)
Estimated Time to arrive at the answer = 45 seconds.
Using Technique
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Assume each option to be the right answer and reverse calculate to check as follows:
Option Age of Dick Age of Tom Age of Tom 20 years back
a. 44 50 30 (multiple of 15)
b. 48 54 34 (not a multiple of 15)
c. 50 56 36 (not a multiple of 15)
d. 52 58 38 (not a multiple of 15)
e. 54 60 40 (not a multiple of 15)
(Note: If you go sequentially taking one option at a time and start with option ‘1’, you do not have to go further as option ‘1’ will give the age of Tom 20 years back as a multiple of 15. No other option leads to a multiple of 15.)
(Ans: 1)
Estimated Time to arrive at the answer = 30 seconds.
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