Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 9)
9.
A does 80% of a work in 20 days. He then calls in B and they together finish the remaining work in 3 days. How long B alone would take to do the whole work?
23 days
37 days
37
40 days
Answer: Option
Explanation:
| Whole work is done by A in |  |
20 x | 5 |  |
= 25 days. |
| 4 |
| Now, | |
1 - | 4 | |
i.e., | 1 | work is done by A and B in 3 days. |
| 5 | 5 |
Whole work will be done by A and B in (3 x 5) = 15 days.
| A's 1 day's work = | 1 | , (A + B)'s 1 day's work = | 1 | . |
| 25 | 15 |
 B's 1 day's work = |
|
1 | - | 1 | |
= | 4 | = | 2 | . |
| 15 | 25 | 150 | 75 |
| So, B alone would do the work in | 75 | = 37 | 1 | days. |
| 2 | 2 |
Discussion:
164 comments Page 17 of 17.
Jay said:
1 decade ago
@shefali..the 15 days is nothing but remaining work probability. 4/5 i.e 80% work is done by A so remaining is 1-(4/5)= 1/5. its same like p+q=1 in probability.
n same like 3*5=15 days
n same like 3*5=15 days
(1)
Shefali said:
1 decade ago
How do we get that A & B together can do work in 15 days?
Snehagoud said:
1 decade ago
A did only 80% of work out of total work in 20 days so
work done by A=80/100=5/4
so total workdone by A=20*5/4
work done by A=80/100=5/4
so total workdone by A=20*5/4
SIVARANJANI said:
1 decade ago
Sorry I can't get it why we should multiply with that 5/4 ?
(2)
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