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.
Shakti said:
1 decade ago
Let total work = 60.
A's effi.=3, same as B and C have 2 and 1.
Then work
1st 2nd 3rd
3 3 6
Total work in 3 days 12 and hence they take 15 days to complete the work(60).
A's effi.=3, same as B and C have 2 and 1.
Then work
1st 2nd 3rd
3 3 6
Total work in 3 days 12 and hence they take 15 days to complete the work(60).
Praveen.M said:
1 decade ago
Hey guys I have done this way, correct me if I'm wrong.
Let total work be 100%.
A does 5%work in a day (1/20*100).
B does 1/30*100 i.e. 3.3%work.
And like wise C does 1.6% of work.
A completes 10% work in 2 days and on 3rd day he is assisted by B and C hence on 3rd day A does 15%of work and total work on 3rd day is 15%+3.3%+1.6% total is 19.9% so total time is 100/19.9*3 = 15.
Let total work be 100%.
A does 5%work in a day (1/20*100).
B does 1/30*100 i.e. 3.3%work.
And like wise C does 1.6% of work.
A completes 10% work in 2 days and on 3rd day he is assisted by B and C hence on 3rd day A does 15%of work and total work on 3rd day is 15%+3.3%+1.6% total is 19.9% so total time is 100/19.9*3 = 15.
Sami said:
1 decade ago
Hi.
Can you explain me that how do you get A's 2 days work?
Can you explain me that how do you get A's 2 days work?
Jansi said:
1 decade ago
@Sami.
Dear friend A is assisted with B & C every 3rd day, Means first 2 days A is doing work lonely.
Dear friend A is assisted with B & C every 3rd day, Means first 2 days A is doing work lonely.
Amey said:
1 decade ago
Why we are multiplying 3 by 5 ?
Randheer said:
1 decade ago
Please anyone can explain what formula we have to use for this problems?
Lalas Hasan said:
1 decade ago
A Little Addition to @Vikas's explanation
A is working alone for two days, 3rd day he is assisted by B and C.
A's 1 day work=1/20.
A working on 2 days=2*1/20=1/10.
A+B+C working on 3rd day, so 1 day of working together = 1/20+1/30+1/60 = 6/60 = 1/10.
So total work done till 3rd day=1/10+1/10=2/10=1/5.
So if in 3 days = 1/5 of work is completed....
Total work is always 1;
So in order to make the value of RHS 1 multiply both side by 5;
Then, 3*5 days = 1/5*5 work will be completed.
= 15 days.
A is working alone for two days, 3rd day he is assisted by B and C.
A's 1 day work=1/20.
A working on 2 days=2*1/20=1/10.
A+B+C working on 3rd day, so 1 day of working together = 1/20+1/30+1/60 = 6/60 = 1/10.
So total work done till 3rd day=1/10+1/10=2/10=1/5.
So if in 3 days = 1/5 of work is completed....
Total work is always 1;
So in order to make the value of RHS 1 multiply both side by 5;
Then, 3*5 days = 1/5*5 work will be completed.
= 15 days.
Ggg said:
1 decade ago
A can do 1/20 of the work per day.
B can do 1/30 of the work per day.
C can do 1/60 of the work per day.
Together, they can do 1/20 + 1/30 + 1/60 of the work per day. But since B and C only help every third day, they can do, on average, 1/20 + 1/3 (1/30 + 1/60) of the work per day.
= 1/20 + 1/3 (1/30 + 1/60).
= 1/20 + 1/3 (3/60).
= 1/20 + 1/3 (1/20).
= 1/20 + 1/60.
= 4/60.
= 1/15.
So if they can do 1/15 of the work per day, they can finish the job in 15 days.
Answer: 15 days.
B can do 1/30 of the work per day.
C can do 1/60 of the work per day.
Together, they can do 1/20 + 1/30 + 1/60 of the work per day. But since B and C only help every third day, they can do, on average, 1/20 + 1/3 (1/30 + 1/60) of the work per day.
= 1/20 + 1/3 (1/30 + 1/60).
= 1/20 + 1/3 (3/60).
= 1/20 + 1/3 (1/20).
= 1/20 + 1/60.
= 4/60.
= 1/15.
So if they can do 1/15 of the work per day, they can finish the job in 15 days.
Answer: 15 days.
Haphyz said:
1 decade ago
I think @Manoj made it simpler and direct. Get the portion of the job that would be completed in 3 days and then keep adding that portion in 3 days interval until you get 1.
TEJAL said:
1 decade ago
I can't understand that how the total work is calculated which is done by A.
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