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 2 of 6.
Sunil kumar said:
1 decade ago
Efficiency ratio is 7:4.
Time ratio is 4:7.
Work ratio is inversely proportional to time ratio.
Here A is more efficient so A's time is less, B is less efficient than a so B take more time than A.
So both take 28 days (7 + 4) 11 ---- 28.
11/7*28 = 11*4 = 44 days.
So answer is 44 days.
Time ratio is 4:7.
Work ratio is inversely proportional to time ratio.
Here A is more efficient so A's time is less, B is less efficient than a so B take more time than A.
So both take 28 days (7 + 4) 11 ---- 28.
11/7*28 = 11*4 = 44 days.
So answer is 44 days.
Nidhi said:
1 decade ago
A and B collectively can do the work in 7 days.
So their one day work is 1/7.
A+B=1/7-- (1).
A is 7/4 times efficient then B which means.
A= (7/4) B.
Or.
B= (4/7) A - (2).
Put the value of (2) in (1).
(4/7) *B+B=1/7.
B=1/11 THIS IS HIS ONE DAY WORK.
ALONE B CAN FINISH IN 11 DAY.
So their one day work is 1/7.
A+B=1/7-- (1).
A is 7/4 times efficient then B which means.
A= (7/4) B.
Or.
B= (4/7) A - (2).
Put the value of (2) in (1).
(4/7) *B+B=1/7.
B=1/11 THIS IS HIS ONE DAY WORK.
ALONE B CAN FINISH IN 11 DAY.
Vembarasi pandiyan said:
1 decade ago
Here efficiency is given so we have to change efficiency into time but in this this why the efficiency is not change I want to know the reason please explain it. 7/4:1=7x:4x this is efficiency 4x:7x this is the time in this question why we are not change the efficiency into time.
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)
ASHRAF said:
9 years ago
Can also do by LCM method A is 1.75 times of effort b ie... 1 3/4 is equal to 1.75...if B is work spree is B then A will be 1.75B is same. So work done by A+B in 7-days is equal to A's work in x days.
So 2.75B * 7 = 1.75B * X,
Solve you get X = 11.
So 2.75B * 7 = 1.75B * X,
Solve you get X = 11.
(1)
Shadab Akhtar said:
9 years ago
@priya & siri, 7/4 is given in question itself, when you will solve the fraction part you will get it.
A+B = 1/7 (given). 1.
A = 7/4*B (given). 2.
B = 4A/7 (from 2).
Put the value of B in eq 1.
A+4A/7 = 1/7.
A = 1/11.
So A will do the work in 11 days.
A+B = 1/7 (given). 1.
A = 7/4*B (given). 2.
B = 4A/7 (from 2).
Put the value of B in eq 1.
A+4A/7 = 1/7.
A = 1/11.
So A will do the work in 11 days.
(2)
Anil kumar reddy said:
9 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.
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)
Krishna mohan said:
10 years ago
Given, A+B = 1/7 ------(1).
And A = 7/4B (A is 13/4 times as efficient as B).
Sub A = 7/4B in (1).
We get B = 4/77---- (2).
Then Sub (2) in (1).
We get A = 1/11 (which means A can complete work in 11 days).
And A = 7/4B (A is 13/4 times as efficient as B).
Sub A = 7/4B in (1).
We get B = 4/77---- (2).
Then Sub (2) in (1).
We get A = 1/11 (which means A can complete work in 11 days).
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)
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