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:
168 comments Page 11 of 17.
Saiteja said:
9 years ago
20 days-80% => 1 day-4%.
In 3 days a+b-20% => 3b=20-3*4% = 8%.
b = 8/3% => 100*8/3 = 37.5.
In 3 days a+b-20% => 3b=20-3*4% = 8%.
b = 8/3% => 100*8/3 = 37.5.
Vijay said:
7 years ago
1day work of A : (1/20)*80/100 = 1/25,
A+B = 3/25 + 3/x=1/5(for 3days).
Find x = 37.5.
A+B = 3/25 + 3/x=1/5(for 3days).
Find x = 37.5.
Balaji said:
1 decade ago
I can't understand the simple step anyone friends tell me (1/15-1/25) please tell me?
Swapraj said:
9 years ago
80%= 4/5.
But, work done by A = 5/4 * 20 why not 4/5 * 20.
Please explain me.
But, work done by A = 5/4 * 20 why not 4/5 * 20.
Please explain me.
Mathi said:
2 decades ago
A = (1/20) * (80/100) = 1/25
1/A + 1/B =1/3(20/100)
1/B=(1/15) - (1/25) =2/75
1/A + 1/B =1/3(20/100)
1/B=(1/15) - (1/25) =2/75
(1)
Selva said:
8 months ago
a = 1/25.
a + b = 1/15.
b = 1/25 - 1/15 = 2/75 = 1/37.5(37.5 days).
a + b = 1/15.
b = 1/25 - 1/15 = 2/75 = 1/37.5(37.5 days).
(7)
Charu said:
1 decade ago
Thanks Bhasker, Ganesh and Mini... Keep up the good work!!! cheers
Kriti said:
1 decade ago
Hey guys 80/100 = 4/5 then why you people multiplying 5/4 * 20?
Prathap said:
1 decade ago
Bhaskar and rajendra you both are explained very well. Thanks.
Jiya said:
10 years ago
Still, I'm not getting why its 5/4*20? Please explain briefly.
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