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 4 of 6.
M.vignesh said:
1 decade ago
A=7/4
B=1
A:B=7/4:1
So A:b=7:4
Total Working Days=7*4=28
a=28/7=4
b=28/4=7
a=a+b
a=4+7=11
A alone=11
B=1
A:B=7/4:1
So A:b=7:4
Total Working Days=7*4=28
a=28/7=4
b=28/4=7
a=a+b
a=4+7=11
A alone=11
Divya said:
1 decade ago
Because a is 7/4 times efficient than b => a= 7/4b
a:b= 7/4b:b (b's get cancelled.)
=> 7/4:1
a:b= 7/4b:b (b's get cancelled.)
=> 7/4:1
Kirshna said:
1 decade ago
How get a:b :: 7/4:1 ?
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.
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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