Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 29)
29.
A and B can do a job together in 7 days. A is 1
times as efficient as B. The same job can be done by A alone in :
times as efficient as B. The same job can be done by A alone in :Answer: Option
Explanation:
| (A's 1 day's work) : (B's 1 day's work) = | 7 | : 1 = 7 : 4. |
| 4 |
Let A's and B's 1 day's work be 7x and 4x respectively.
| Then, 7x + 4x = | 1 |  11x = |
1 | x = |
1 | . |
| 7 | 7 | 77 |
 A's 1 day's work = |
 |
1 | x 7 |  |
= | 1 | . |
| 77 | 11 |
Discussion:
54 comments Page 3 of 6.
Anil kumar reddy said:
10 years ago
a + b = 7 days.
a = 7/4 * b.
Therefore a + 4/7a - 7 days {since men is inversely proportional to days}.
11a/7 - 7 days for getting a divide with 11/7 and another side multiply with 11/7 then we get 11 days to get complete by alone.
a = 7/4 * b.
Therefore a + 4/7a - 7 days {since men is inversely proportional to days}.
11a/7 - 7 days for getting a divide with 11/7 and another side multiply with 11/7 then we get 11 days to get complete by alone.
Vaibhav jain said:
10 years ago
Let,
A = x.
B = 7/4x.
Total work = 7x (i.e. Lcm of A &B).
A's one day work = 7.
B's one day work = 4.
(A + B)'s one day work = 11.
As we know that total work we have 7x.
Using formula of work --->(total work/(A+B) one day work) = (A+B) total work.
7x/11 = 7--->x=7*11/7--> x = 11 i.e total days of x.
A = x.
B = 7/4x.
Total work = 7x (i.e. Lcm of A &B).
A's one day work = 7.
B's one day work = 4.
(A + B)'s one day work = 11.
As we know that total work we have 7x.
Using formula of work --->(total work/(A+B) one day work) = (A+B) total work.
7x/11 = 7--->x=7*11/7--> x = 11 i.e total days of x.
Bharathi said:
9 years ago
It's easy to understand. Thanks @Kuntal.
Adithya vinay kumar said:
1 decade ago
How come efficiency is directly proportional to the no of days worked?
Swapna said:
9 years ago
7+4=11......28 ,7....? 11/7*28 = 44 ans.
Padma said:
9 years ago
Why have they taken efficiency as such without converting it to number of days?
Prabhu said:
9 years ago
Nice explanation @Jimmy John.
Mohan said:
2 days ago
A and B can do a job together in 7 days.
A is 1⅓ times as efficient as B.
Efficiency ratio:
A : B = 4 : 3.
Total efficiency:
4 + 3 = 7 units/day.
Since they complete the work in 7 days:
Total work = 7 × 7 = 49 units.
A's efficiency = 4 units/day.
Time taken by A alone:
Time = Total Work ÷ A's Efficiency
Time = 49 ÷ 4.
Time = 12¼ days.
Answer: 12¼ days.
A is 1⅓ times as efficient as B.
Efficiency ratio:
A : B = 4 : 3.
Total efficiency:
4 + 3 = 7 units/day.
Since they complete the work in 7 days:
Total work = 7 × 7 = 49 units.
A's efficiency = 4 units/day.
Time taken by A alone:
Time = Total Work ÷ A's Efficiency
Time = 49 ÷ 4.
Time = 12¼ days.
Answer: 12¼ days.
SHIVAM RANA said:
1 decade ago
As A = 7/4B-------(1).
=> A+B GIVES WORK DONE IN 7 DAYS.
=> Unity gives that work in 7*(A+B) DAYS.
=> Using (1).
=> A gives that work in (7*(A+4/7A))/A DAYS.
=> 11 DAYS.
=> A+B GIVES WORK DONE IN 7 DAYS.
=> Unity gives that work in 7*(A+B) DAYS.
=> Using (1).
=> A gives that work in (7*(A+4/7A))/A DAYS.
=> 11 DAYS.
Kirshna said:
2 decades ago
How get a:b :: 7/4:1 ?
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