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 6 of 36.
Sarathy said:
9 years ago
A's total work = 1.
A's 1 day work = 1/20 = 0.05.
B's 1 day work = 1/30 = 0.03.
c's 1 day work = 1/60 = 0.01.
B + C combined work together = 0.03 + 0.01 = 0.04.
A's 3 day work = 0.05 + 0.05 + 0.05 + 0.04 = 0.19.
If answer is 15 means = 5 * (0.19) = 0.95 remaining 0.05.
So, the answer is wrong.
In 16th day = (15days work + A's one day work).
= (0.95 + 0.05),
= 1.
So, 16 days is the correct answer.
A's 1 day work = 1/20 = 0.05.
B's 1 day work = 1/30 = 0.03.
c's 1 day work = 1/60 = 0.01.
B + C combined work together = 0.03 + 0.01 = 0.04.
A's 3 day work = 0.05 + 0.05 + 0.05 + 0.04 = 0.19.
If answer is 15 means = 5 * (0.19) = 0.95 remaining 0.05.
So, the answer is wrong.
In 16th day = (15days work + A's one day work).
= (0.95 + 0.05),
= 1.
So, 16 days is the correct answer.
Sunil_ said:
5 years ago
A work in one day = 1/20,
B work in one day = 1/30,
C work in one day = 1/60.
As A work for 2 days and then on third day B and C do work.
Total work done in three days = A 3 days work+B 1-day work+ C one day work,
= 3/20 + 1/30 + 1/60,
= 9/60 + 2/60 + 1/60
= 12/60.
Total work is done in three days =1/5.
3 = 1/5part.
Let x days required to complete work = 1 part.
3/x = 1/5/1.
x = 3 * 5 = 15 days.
B work in one day = 1/30,
C work in one day = 1/60.
As A work for 2 days and then on third day B and C do work.
Total work done in three days = A 3 days work+B 1-day work+ C one day work,
= 3/20 + 1/30 + 1/60,
= 9/60 + 2/60 + 1/60
= 12/60.
Total work is done in three days =1/5.
3 = 1/5part.
Let x days required to complete work = 1 part.
3/x = 1/5/1.
x = 3 * 5 = 15 days.
(1)
Chittu said:
10 years ago
B and C can complete this work in 20 days.
B and C one day work will be = (1/20).
Instead of assuming every third day B and C will join A in work, let us reduce the efficiency of B and C by 3 so this makes B and C one day as 1/60.
So now doing the calculations.
(1/20)+(1/60) = 1/15. Hence they can complete the work in 15 days.
Please let me know in case of any clarifications needed.
B and C one day work will be = (1/20).
Instead of assuming every third day B and C will join A in work, let us reduce the efficiency of B and C by 3 so this makes B and C one day as 1/60.
So now doing the calculations.
(1/20)+(1/60) = 1/15. Hence they can complete the work in 15 days.
Please let me know in case of any clarifications needed.
Kumar said:
1 decade ago
@Preethi
Finally we got the answer 1/5->work completed in 3 days clear upto here.Coming to your doubt we have to know the full work completed in no of days 1/5th work == 3days=1/5th work Just make above Rhs as 1 Full work == 3*? =1/5*5
== 3*5 =1/5*5
1 Full work in 15 days == 15 =1
Hope your doubt is cleared.
Finally we got the answer 1/5->work completed in 3 days clear upto here.Coming to your doubt we have to know the full work completed in no of days 1/5th work == 3days=1/5th work Just make above Rhs as 1 Full work == 3*? =1/5*5
== 3*5 =1/5*5
1 Full work in 15 days == 15 =1
Hope your doubt is cleared.
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'.
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.
Raman(UIET,KUK) said:
1 decade ago
Guys check dis out........
as we know A will be assist by B & C every third day, so first two day A will work again
A's 1st day of work = 1/20
A's 2nd day of work = 1/20
(A+B+C)'s 3rd day of work = 1/20+1/30+1/60=1/10
total work of 3 days = 1/20+1/20+1/10=1/5
hence,
3 days of work = 1/5
1 day of work will be=1/5*3
=1/15
so work will complete in 15 days
as we know A will be assist by B & C every third day, so first two day A will work again
A's 1st day of work = 1/20
A's 2nd day of work = 1/20
(A+B+C)'s 3rd day of work = 1/20+1/30+1/60=1/10
total work of 3 days = 1/20+1/20+1/10=1/5
hence,
3 days of work = 1/5
1 day of work will be=1/5*3
=1/15
so work will complete in 15 days
(1)
Vikas said:
1 decade ago
Answer Explained:
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....
Than, 3*5 days = 1/5*5 work will be completed.
=15days
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....
Than, 3*5 days = 1/5*5 work will be completed.
=15days
(4)
Ananthu said:
4 years ago
For the peopel who are confused with last step.
We knew that 3 days work is 1/5.. the remaining work is 1-1/5=4/5.. ie already worked 3 days here.
Then we are calculating that how many 3 days are required to complete the remaining work 4/5.
Ie 4/5/1/5 = 4/5 * 5/1 = 4.. 4 (three days required).
ie 4*3 = 12 we already worked 3 days then total days will be 12 + 3 = 15.
We knew that 3 days work is 1/5.. the remaining work is 1-1/5=4/5.. ie already worked 3 days here.
Then we are calculating that how many 3 days are required to complete the remaining work 4/5.
Ie 4/5/1/5 = 4/5 * 5/1 = 4.. 4 (three days required).
ie 4*3 = 12 we already worked 3 days then total days will be 12 + 3 = 15.
(8)
Sawaira ikram said:
4 years ago
Work done by A = 1/20.
Work done by B= 1/30.
Work done by C= 1/60.
Now, work done by A in 2 days is= (1/20) * 2 = 1/10.
And work done by A,B,C in one day= 1/20 + 1/30 + 1/60 = (3+2+1)/60 = 6/60 = 1/10.
And the work done in first 3 days = 1/10 + 1/10 = 1/5.
So we can say that 1/5 part of work is done= in 3 days.
And 1 complete work is done in=. 3/(1/5) = 3*5 = 15 days.
Work done by B= 1/30.
Work done by C= 1/60.
Now, work done by A in 2 days is= (1/20) * 2 = 1/10.
And work done by A,B,C in one day= 1/20 + 1/30 + 1/60 = (3+2+1)/60 = 6/60 = 1/10.
And the work done in first 3 days = 1/10 + 1/10 = 1/5.
So we can say that 1/5 part of work is done= in 3 days.
And 1 complete work is done in=. 3/(1/5) = 3*5 = 15 days.
(126)
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers