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:
357 comments Page 16 of 36.
Jenni said:
10 years ago
How to multiply and solve this equation?
1/20 + 1/30 + 1/60
1/20 + 1/30 + 1/60
Jemish said:
10 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:
10 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:
10 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:
10 years ago
Got it on 3 day B & C is helping A.
Shridhar said:
10 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.
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