Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 13)
13.
A and B can together finish a work 30 days. They worked together for 20 days and then B left. After another 20 days, A finished the remaining work. In how many days A alone can finish the work?
Answer: Option
Explanation:
| (A + B)'s 20 day's work = |  |
1 | x 20 |  |
= | 2 | . |
| 30 | 3 |
| Remaining work = | |
1 - | 2 | |
= | 1 | . |
| 3 | 3 |
| Now, | 1 | work is done by A in 20 days. |
| 3 |
Therefore, the whole work will be done by A in (20 x 3) = 60 days.
Discussion:
64 comments Page 4 of 7.
Sinchana Shettar said:
5 years ago
Please, Explain this with LCM method.
Saloni panigrahi said:
5 years ago
E * t = w.
Since e is inverse of t so 20 becomes 1/20.
Now 1/20*t=1/3 since we have to find the time taken so,
T =20/1/3 HENCE T= 60 because in LHS it is multiplication so after coming to RHS it will divide.
Since e is inverse of t so 20 becomes 1/20.
Now 1/20*t=1/3 since we have to find the time taken so,
T =20/1/3 HENCE T= 60 because in LHS it is multiplication so after coming to RHS it will divide.
Gautam Bajaj said:
3 weeks ago
Simplest and straightforward solution:
Let us assume x is the efficiency of A ( units done per day )
y is the efficiency of B ( units done per day )
According to the question;
The total work to be done is the same in any case, whether they do it together or separately.
Work = efficiency * time.
ATQ;
(x + y) * 30 = (x+y)*20 + 20x.
Solve and get x = y.
Which means the efficiency of both A and B are same.
( also could have made a wild guess to assume 1 unit per day to be the efficiency of both it satisfies the constraints in the given question)
Now, since the efficiency of both is 1 unit per day total work to be done = 60 units.
The efficiency of A is 1 unit per day, so it will take 60 days for A to complete the work.
Let us assume x is the efficiency of A ( units done per day )
y is the efficiency of B ( units done per day )
According to the question;
The total work to be done is the same in any case, whether they do it together or separately.
Work = efficiency * time.
ATQ;
(x + y) * 30 = (x+y)*20 + 20x.
Solve and get x = y.
Which means the efficiency of both A and B are same.
( also could have made a wild guess to assume 1 unit per day to be the efficiency of both it satisfies the constraints in the given question)
Now, since the efficiency of both is 1 unit per day total work to be done = 60 units.
The efficiency of A is 1 unit per day, so it will take 60 days for A to complete the work.
Balaji rajendran said:
1 decade ago
@Deepak yadav.
In this problem A can finish 10 days work in 20 days so if he left alone to do a 30 days work, he will take 60 days to finish the work.
In this problem A can finish 10 days work in 20 days so if he left alone to do a 30 days work, he will take 60 days to finish the work.
Asha said:
1 decade ago
Hey @ankush
The question here is that in how many days A alone can do the entire work..
So its very simple 1/3 work done in 20 days, 2/3 work in 20*2=40 days and 3/3 (i.e. 1)= 20*3=60 days.
The question here is that in how many days A alone can do the entire work..
So its very simple 1/3 work done in 20 days, 2/3 work in 20*2=40 days and 3/3 (i.e. 1)= 20*3=60 days.
Srishailam said:
1 decade ago
Am not understanding this problem any body please help me.
How A work come 20 days. Explain ?
How A work come 20 days. Explain ?
Dhruv said:
1 decade ago
How come 1/3 work is done in 20 days should the work in 20 days not be 2/3?
Avi said:
1 decade ago
A & B together works for 30 days
so, (A & B)'s 1 day work= 1/30
A&B worked for 20 days together
it is said after working together for 20 days b left
so, (A&B)'s work for 20 days together = (1/30)x20=2/3
remaining work that is to be done =1-2/3=1/3
1/3 work is done in 20 days
1 work i.e; complete work would be done in 20/(1/3)=20x3=60 days
so, (A & B)'s 1 day work= 1/30
A&B worked for 20 days together
it is said after working together for 20 days b left
so, (A&B)'s work for 20 days together = (1/30)x20=2/3
remaining work that is to be done =1-2/3=1/3
1/3 work is done in 20 days
1 work i.e; complete work would be done in 20/(1/3)=20x3=60 days
Kulbhushan said:
1 decade ago
Hi, how we calculated that 1/3 work in 20 days?
Manikandan said:
1 decade ago
@kulbhushan
Already 20 days work finished by A and B.Remaining 10 days work done by A in 20 days. If A alone able to finish 30 days work in 60days.
Already 20 days work finished by A and B.Remaining 10 days work done by A in 20 days. If A alone able to finish 30 days work in 60days.
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