Here’s and example of a SMART MATH problem for RATIO PROPORTION.
Problem
A can do a piece of work in 12 days. A and B together do the work in 8 days. How long would B alone take to complete the work?
- 8 days
- 10 days
- 15 days
- 18 days
- 24 days
The Usual Method
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A in one day will finish th of the work.
Let B finish th of the work in one day.
Hence,
Days
(Ans: 5)
Estimated Time to arrive at the answer = 45 seconds.
Using Technique
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Should B take 12 days working alone, than A and B working together would take 6 days. But A and B together actually take 8 days; hence B would take more than 12 days to finish the work working alone. This eliminates options ‘1’ and ‘2’
Also note that the difference between 6 days and actual 8 days is that of 2 days. Simply multiplying 2 with 12 we get 24 days which is the answer.
(Ans: 5)
Estimated Time to arrive at the answer = 10 seconds.
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