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 13 of 17.
Buela said:
8 years ago
Thank you @Vishnu.
Vishnu said:
8 years ago
Very simple,
A's 1 day work = (0.8/20).
(a+b)'s 1 day work = (0.2/3).
So, b's work = (0.2/3) - (0.8/20).
= 2/75.
Therefore days taken by B = 75/2 = 37 1/2.
A's 1 day work = (0.8/20).
(a+b)'s 1 day work = (0.2/3).
So, b's work = (0.2/3) - (0.8/20).
= 2/75.
Therefore days taken by B = 75/2 = 37 1/2.
Saiteja said:
8 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.
Bharath said:
8 years ago
Work done by A in 20 days = 80/100 = 8/10 = 4/5
Work done by A in 1 day = (4/5) / 20 = 4/100 = 1/25 --- (1)
Work done by A and B in 3 days = 20/100 = 1/5 (Because remaining 20% is done in 3 days by A and B)
Work done by A and B in 1 day = 1/15 ---(2)
Work done by B in 1 day = 1/15 " 1/25 = 2/75
=> B can complete the work in 75/2 days = 37 (1/2) days.
Work done by A in 1 day = (4/5) / 20 = 4/100 = 1/25 --- (1)
Work done by A and B in 3 days = 20/100 = 1/5 (Because remaining 20% is done in 3 days by A and B)
Work done by A and B in 1 day = 1/15 ---(2)
Work done by B in 1 day = 1/15 " 1/25 = 2/75
=> B can complete the work in 75/2 days = 37 (1/2) days.
Nani said:
8 years ago
Good explanation, thank you @Rajendra.
Ruchi said:
8 years ago
Nice method, Thanks @Suganya.
Khan Singh John said:
8 years ago
A complete 80 work on 20 day then efficiency is 4.
A & B complete remaining 20 work in 3 days.
So A works 4*3=12 in 3 days.
12+80=92.
and B complete 8 works in 3 days.
and efficiency of B is 8/3.
Hence B will complete whole work in 100/(8/3) = 75/2.
A & B complete remaining 20 work in 3 days.
So A works 4*3=12 in 3 days.
12+80=92.
and B complete 8 works in 3 days.
and efficiency of B is 8/3.
Hence B will complete whole work in 100/(8/3) = 75/2.
SHIMEGHA.T.C said:
8 years ago
3(A+B)20%. = 80%(20A),
3/20*100. = 20/80*100A
15days(a+b). = 25 days A alone
B alone work = 1/25-1/15 = 2/75; 75/2.
3/20*100. = 20/80*100A
15days(a+b). = 25 days A alone
B alone work = 1/25-1/15 = 2/75; 75/2.
Surya said:
8 years ago
How 1-4/5? Please explain it.
Gowtham said:
8 years ago
80/100 is 4/5 then how you get it as (20*5/4) =25?
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