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.
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 :).
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.
Girish said:
1 decade ago
Why we should multiply by 7 at the end ?
THIVYA 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 than B which means.
A = (7/4)B ----------(2).
or
B = (4/7)A ------------(2).
Put 2 int 1 eq,
A+(4/7)A = 1/7.
A(11/7) = 1/7.
SO,
A CAN COMPLETE THE PIECE OF WORK IN 11 DAYS.
so their one day work is 1/7.
A+B = 1/7-------(1).
A is 7/4 times efficient than B which means.
A = (7/4)B ----------(2).
or
B = (4/7)A ------------(2).
Put 2 int 1 eq,
A+(4/7)A = 1/7.
A(11/7) = 1/7.
SO,
A CAN COMPLETE THE PIECE OF WORK IN 11 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.
Chara said:
1 decade ago
A's working capacity = X.
B's working capacity = Y.
Given, X + Y = 1/30 ................equation(1).
Also, X = 7/4 Y
i.e.. Y= 4/7 X .................equation (2).
PUTTING Y=4/7X from eqtn (2) in Eqtn(1), we get,
X= 1/11.
i.e.. A working capacity is 1/11( interpretation: "A" can do 1 work in 11 days).
B's working capacity = Y.
Given, X + Y = 1/30 ................equation(1).
Also, X = 7/4 Y
i.e.. Y= 4/7 X .................equation (2).
PUTTING Y=4/7X from eqtn (2) in Eqtn(1), we get,
X= 1/11.
i.e.. A working capacity is 1/11( interpretation: "A" can do 1 work in 11 days).
Divi said:
1 decade ago
A is 7/4 efficient than B means A=7/4B =>B=4/7A.
A and B together can complete the work in 7 days.
[i.e.Time is directly proportional to work => 7days=work => 1 day=1/7th work].
So,
A + B = 1/7.
A + 4/7A= 1/7.
11/7A = 1/7.
A = 1/11.
Hence, A alone can work for 11 days.
A and B together can complete the work in 7 days.
[i.e.Time is directly proportional to work => 7days=work => 1 day=1/7th work].
So,
A + B = 1/7.
A + 4/7A= 1/7.
11/7A = 1/7.
A = 1/11.
Hence, A alone can work for 11 days.
Pari said:
1 decade ago
GIVEN : A=7/4B, THEREFORE B = 4/7A.
A + B = 1/7.
A + 4/7A = 1/7.
11/7A = 1/7.
A = I/7*7/11 = 1/11.
Hence 11 days.
Hope this is a correct way.
A + B = 1/7.
A + 4/7A = 1/7.
11/7A = 1/7.
A = I/7*7/11 = 1/11.
Hence 11 days.
Hope this is a correct way.
Raj said:
1 decade ago
How we get A =7/4? Please help me.
Iovd said:
1 decade ago
@Raj.
They given 1*3/4 in example after solving it we get 7/4(4*1+3).
They given 1*3/4 in example after solving it we get 7/4(4*1+3).
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