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.
Vams'trick said:
8 years ago
B complete work in days = X.
A take days = 4X/7,
A+B work in 1 day = 7/4X + 1/X,
But from problem it is 1/7,
7/4X + 1/X = 1/7,
X =77/4 = B,
A = 4X/7= 4/7 * 77/4 = 11.
A take days = 4X/7,
A+B work in 1 day = 7/4X + 1/X,
But from problem it is 1/7,
7/4X + 1/X = 1/7,
X =77/4 = B,
A = 4X/7= 4/7 * 77/4 = 11.
(1)
Sm Jahid said:
9 years ago
Let,
A do the job = X day.
and B do the job = 7X/4.
By the question,
1/X+4/7X = 1/7,
=> 7+4/7X = 1/7,
=> 7X = 77,
=> X = 11.
So A do the job in 11 days.
A do the job = X day.
and B do the job = 7X/4.
By the question,
1/X+4/7X = 1/7,
=> 7+4/7X = 1/7,
=> 7X = 77,
=> X = 11.
So A do the job in 11 days.
(1)
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)
Jimmy John said:
1 decade ago
A+B=1/7
7A+7B=1-----1
A=7/4B
4A=7B-----2
sub 2 in 1
7A+4A=1 (Since 7B=4A)
therefore 11A=1
A=1/11
therefore A can finish in 11 days
7A+7B=1-----1
A=7/4B
4A=7B-----2
sub 2 in 1
7A+4A=1 (Since 7B=4A)
therefore 11A=1
A=1/11
therefore A can finish in 11 days
(1)
Padma said:
8 years ago
Why have they taken efficiency as such without converting it to number of days?
Kriti said:
9 years ago
Guys I am not getting the concept of equation 1 and 2 please any one explain me in detail, please.
Pradeep Oram said:
1 decade ago
Given: A+B = 1/7......(1).
And A = 7/4B (efficient than B).
Put in(1). We get.
B=4/77(work of B).
Then,
Work of A = (1/7)-(4/77) = 7/77 = 1/11 (from eq.(1)).
So, A finish job in 11 days.
And A = 7/4B (efficient than B).
Put in(1). We get.
B=4/77(work of B).
Then,
Work of A = (1/7)-(4/77) = 7/77 = 1/11 (from eq.(1)).
So, A finish job in 11 days.
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.
Vaibhav jain said:
9 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.
Torres Dungs said:
1 decade ago
I think this would be an easy approach:
A=7/4B (A is as efficient as 1*3/4 times as B).
=> On cross multiplying we get, 4A=7B-----------> 1.
=> From question, A+B=1/7 (A,B is one days work so equating to 1/7).
Therefore again cross multiply,
We get, 7A+7B = 1.
=>from 1, we have 4A=7B.
So substitute 4A in 7B.
We get,
7A+4A=1 ==>11A=1===> A=1/11(which is A's one day's work).
Hence,
Total days A need==> 11 days.
Hope you'd have undersTood :).
A=7/4B (A is as efficient as 1*3/4 times as B).
=> On cross multiplying we get, 4A=7B-----------> 1.
=> From question, A+B=1/7 (A,B is one days work so equating to 1/7).
Therefore again cross multiply,
We get, 7A+7B = 1.
=>from 1, we have 4A=7B.
So substitute 4A in 7B.
We get,
7A+4A=1 ==>11A=1===> A=1/11(which is A's one day's work).
Hence,
Total days A need==> 11 days.
Hope you'd have undersTood :).
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