Question Detail
Worker A takes 8 hours to do a job. Worker B takes 10 hours to do a job. How long should it take both A and B, working together to do same job.
- \begin{aligned} \frac{4}{9} \end{aligned}
- \begin{aligned} 2\frac{4}{9} \end{aligned}
- \begin{aligned} 3\frac{4}{9} \end{aligned}
- \begin{aligned} 4\frac{4}{9} \end{aligned}
Answer: Option D
Explanation:
In this type of questions, first we need to calculate 1 hours work, then their collective work as,
A's 1 hour work is 1/8
B's 1 hour work is 1/10
(A+B)'s 1 hour work = 1/8 + 1/10
= 9/40
So both will finish the work in 40/9 hours
= \begin{aligned} 4\frac{4}{9} \end{aligned}
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Dixit Nayak 9 years ago
Two workers undertake to do a job. 2nd worker
started two hours after the 1st. 5 hours after the 2nd worker
started the work, only 11/20 work was done. In how
many hours they can complete the work independently, if it is known that 1st
worker did 60% of the total work and 2nd worker did the rest??? -
Shubham sanware 9 years ago
How 1 hour work is 1/8 ?
-
Awais 12 years ago
where is came from?? means 40/9?? and how is it done 4/4/9
mastguru 12 years ago replied
Hello Awais,
as we calculated that work done by A and B in 1 hour is 9/40 hour
It means both will finish work in 40/9 hour, here denominator becomes numerator and numerator become denominator.
or say if You can finish a task in 8 days, it means you will finish 1/8 in 1 day, right.
Also if you can finish 1/8 in 1 day then it means you will finish it in 8 days. so it is inverse of that.
In same way we got 40/9 from 9/40
also 4(4/9) = 40/9,
As options were given in this format so we had to break it in this form.
In this type of form,
we calculate as,
(4*denominator+numerator)/denominator,
i.e. (4*9+4)/9 = 40/9
Hope it helps.
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