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:
53 comments Page 6 of 6.
Lingaraj Behera said:
3 years ago
(A+B) 1day work is 1/7 --------------> (1)
Let 1-day work of A is 1/A, such as 1-day work of B is 1/B
Then 1/A + 1/B = 1A + 1/A * 7/4.
1/A + 4/7A = 11/7A--------------(2)
11/7A = 1/7,
7A = 77,
A = 11.
Let 1-day work of A is 1/A, such as 1-day work of B is 1/B
Then 1/A + 1/B = 1A + 1/A * 7/4.
1/A + 4/7A = 11/7A--------------(2)
11/7A = 1/7,
7A = 77,
A = 11.
(6)
Menya Alex said:
3 years ago
Let A+B = 7 days.
Then (A+B)'s one day work = 1/7,
Let X represent B,
=> 7/4X + X = 1/7,
=>7X + 4X = 4/7,
=>11X = 4/7,
=>X = 4/77,
But A = 7/4X.
=> A = (7/4*4/77),
=> A = 1/11,
Giving us 11 days.
Then (A+B)'s one day work = 1/7,
Let X represent B,
=> 7/4X + X = 1/7,
=>7X + 4X = 4/7,
=>11X = 4/7,
=>X = 4/77,
But A = 7/4X.
=> A = (7/4*4/77),
=> A = 1/11,
Giving us 11 days.
(10)
Prashanth said:
1 year ago
A = 1.75 times efficient means
B = 1.
Together completed = 7days.
If B works alone;
1 * 7 = 7days.
Remaining A work also done by B (efficiency of A) 1.75 * 7 =12.25 days
Total days taken by B = 7 + 12.25 = 19.25days;
If A alone 19.25/1.75(efficiency of A).
= 11 days.
B = 1.
Together completed = 7days.
If B works alone;
1 * 7 = 7days.
Remaining A work also done by B (efficiency of A) 1.75 * 7 =12.25 days
Total days taken by B = 7 + 12.25 = 19.25days;
If A alone 19.25/1.75(efficiency of A).
= 11 days.
(4)
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