Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 3)
3.
A, B and C can do a piece of work in 20, 30 and 60 days respectively. In how many days can A do the work if he is assisted by B and C on every third day?
Answer: Option
Explanation:
| A's 2 day's work = |  |
1 | x 2 |  |
= | 1 | . |
| 20 | 10 |
| (A + B + C)'s 1 day's work = | |
1 | + | 1 | + | 1 | |
= | 6 | = | 1 | . |
| 20 | 30 | 60 | 60 | 10 |
| Work done in 3 days = | |
1 | + | 1 | |
= | 1 | . |
| 10 | 10 | 5 |
| Now, | 1 | work is done in 3 days. |
| 5 |
Whole work will be done in (3 x 5) = 15 days.
Discussion:
356 comments Page 16 of 36.
Jemish said:
9 years ago
My new approach to explaining the answer.
=> A is working continuously.
=> B and C join at every 3rd day.
A's efficiency is used as it is,
But B and C's efficiency is used 1/3rd part considering a task.
thus,
A--> 1/20
B--> 1/3 * (1/30)
c--> 1/3 * (1/60)
Now simple.
To find out days required = 1/20 + 1/90 + 1/180 = 1/15.
Answer: 15 days required.
=> A is working continuously.
=> B and C join at every 3rd day.
A's efficiency is used as it is,
But B and C's efficiency is used 1/3rd part considering a task.
thus,
A--> 1/20
B--> 1/3 * (1/30)
c--> 1/3 * (1/60)
Now simple.
To find out days required = 1/20 + 1/90 + 1/180 = 1/15.
Answer: 15 days required.
Shruthi said:
9 years ago
Please explain the 2nd step => (A + B + C) 's 1 day's work.
How it becomes 6/60.
How it becomes 6/60.
Ompal. said:
9 years ago
A, B, and C person can a do work 20, 40 and 60 days respectivily. When they works alternative. They compeleted work how many days.
Shridhar said:
9 years ago
Got it on 3 day B & C is helping A.
Shridhar said:
9 years ago
A as done the work for 2 days, he is asserted to B and C in 3rd, he as not done the work at 3rd day. Then why 1/20 + 1/30 + 1/60?
Sudhansu sekhar said:
10 years ago
Why applied 1/10 + 1/10?
Samrat said:
10 years ago
Note: A alone can do its work in 20 days.
So A can do the work in 1 day is 1/20.
2nd day A can do work = (1/20)2 = 1/10.
3rd day A, B and C work together.
Therefore A's 1 day work = 1/20, B's 1 day work = 1/30, C's 1 day work = 1/60.
Together A, B and C do work in 1 day = 1/20 + 1/30 + 1/60.
= (3+2+1)/60.
= 6/60 = 1/10.
So after 3 days A's done = 1/10 + 1/10.
= 2/10 = 1/5.
= (1/5)X days = 1.
X = 5.
1/5 work = 3 days.
(1/5)X days = (3)5 days = 15 days.
So A can do the work in 1 day is 1/20.
2nd day A can do work = (1/20)2 = 1/10.
3rd day A, B and C work together.
Therefore A's 1 day work = 1/20, B's 1 day work = 1/30, C's 1 day work = 1/60.
Together A, B and C do work in 1 day = 1/20 + 1/30 + 1/60.
= (3+2+1)/60.
= 6/60 = 1/10.
So after 3 days A's done = 1/10 + 1/10.
= 2/10 = 1/5.
= (1/5)X days = 1.
X = 5.
1/5 work = 3 days.
(1/5)X days = (3)5 days = 15 days.
Ganesh said:
10 years ago
Total work = 60 units (lcm of 20, 30 and 60).
A completes work in 20 days. It means 3 units a day.
B completes work In 30 days. It means 2 units a day.
C completes work in 60 days. It means 1 unit a day.
A is working 2 days alone. It means 3+3 = 6 units is completed.
On third day B and C helping A.
It means on third day 3 +2+1 = 6 units of work is completed.
It means for 3 days 12 units of work is completed.
For 60 units?
60*3/12 = 15.
A completes work in 20 days. It means 3 units a day.
B completes work In 30 days. It means 2 units a day.
C completes work in 60 days. It means 1 unit a day.
A is working 2 days alone. It means 3+3 = 6 units is completed.
On third day B and C helping A.
It means on third day 3 +2+1 = 6 units of work is completed.
It means for 3 days 12 units of work is completed.
For 60 units?
60*3/12 = 15.
Jitesh said:
10 years ago
A = 20.
B = 30.
C = 60.
LCM is 60 so a do the work in 1 day is 3 unit B is doing work in 1 day is 2 unit and C is 1 unit.
1st (A) day = 3.
2nd (A) day = 3.
3rd (A+B+C) day = 3+2+1 = 6.
Total work done in 3 days is 12 unit. So for 60 unit (60/12 = 5).
5*3 days = 15 days.
B = 30.
C = 60.
LCM is 60 so a do the work in 1 day is 3 unit B is doing work in 1 day is 2 unit and C is 1 unit.
1st (A) day = 3.
2nd (A) day = 3.
3rd (A+B+C) day = 3+2+1 = 6.
Total work done in 3 days is 12 unit. So for 60 unit (60/12 = 5).
5*3 days = 15 days.
Teja said:
10 years ago
This is question which is completely related to alternate days.
In alternate days question whenever work done is not given you have to take it as '1'.
Here we got that 1/5 of the work is done in 3 days which means 1/5 work=3 days.
1=how many days?
Cross multiply, you get days=15.
This concept works for all of the alternate days question. When ever work is not given take it as '1'.
In alternate days question whenever work done is not given you have to take it as '1'.
Here we got that 1/5 of the work is done in 3 days which means 1/5 work=3 days.
1=how many days?
Cross multiply, you get days=15.
This concept works for all of the alternate days question. When ever work is not given take it as '1'.
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