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 22 of 36.
Garima Yadav said:
1 decade ago
I haven't got it. Can anyone please help me for this?
Ranju said:
1 decade ago
(A+B+C)'s 1 day of work is (1/20+1/30+1/60) = 1/10.
A's 2 days of work is (1/20 X 2) = 1/10.
As on the third day A is assisted by B and C.
=> A's 2 days of work + On 3rd day A is assisted by B and C i.e. (A+B+C) 's 1 day of work.
1/10 + 1/10 = 2/10 = 1/5.
As 1/5 part of work is done in 3 days.
Therefore 1 part of work is done in 3 X 5 = 15 days.
A's 2 days of work is (1/20 X 2) = 1/10.
As on the third day A is assisted by B and C.
=> A's 2 days of work + On 3rd day A is assisted by B and C i.e. (A+B+C) 's 1 day of work.
1/10 + 1/10 = 2/10 = 1/5.
As 1/5 part of work is done in 3 days.
Therefore 1 part of work is done in 3 X 5 = 15 days.
Nandha said:
1 decade ago
@Ajit.
A do a work two days independently, so (1/20+1/20) = 1/10 instead of they taken (1/20*2).
A do a work two days independently, so (1/20+1/20) = 1/10 instead of they taken (1/20*2).
Deepti said:
1 decade ago
Its written every 3rd day NOT First 3 days. Therefore the answer is as below:
(A+B+C)'s 1 day work = (1/20 + 1/30 + 1/60) = 1/10.
=> They all take 10 days to complete their work together.
Out of those 10 days, 3th, 6th and 9th are the 3rd days. In total B and C can help A for only 3 days.
Therefore, (A's 1 days work) + (B+C) 1 day work*3 = 1/20 + (1/30+1/60) *3 = 4/20 = 1/5.
If 1/5 is the work in 3 days, Then complete work done = 5*3 = 15.
Ans: 15 days.
(A+B+C)'s 1 day work = (1/20 + 1/30 + 1/60) = 1/10.
=> They all take 10 days to complete their work together.
Out of those 10 days, 3th, 6th and 9th are the 3rd days. In total B and C can help A for only 3 days.
Therefore, (A's 1 days work) + (B+C) 1 day work*3 = 1/20 + (1/30+1/60) *3 = 4/20 = 1/5.
If 1/5 is the work in 3 days, Then complete work done = 5*3 = 15.
Ans: 15 days.
Vijay said:
1 decade ago
B and C joined with A for every 3 days.
So their (A,B,C) 3 days work is == (A's 2 days work i.e. [1/10]) + (A+B+C 's 1 day work i.e [1/10]).
= 1/10+1/10 = 1/5.
So for 3 days 1/5 work is done.
So total work will complete in 15 days.
So their (A,B,C) 3 days work is == (A's 2 days work i.e. [1/10]) + (A+B+C 's 1 day work i.e [1/10]).
= 1/10+1/10 = 1/5.
So for 3 days 1/5 work is done.
So total work will complete in 15 days.
Ajit said:
1 decade ago
Why multiply 1/20*2?
Mir sakib said:
1 decade ago
What is its mean every third day?
Chitra said:
1 decade ago
Work done in 3 days = 1/5.
Work done in next 3 days = 1/5+1/5.
Work done in 5 days = 1/5+1/5+1/5+1/5+1/5 = 5/5 = 1 (task completed).
Hence 3*5 is used.
Work done in next 3 days = 1/5+1/5.
Work done in 5 days = 1/5+1/5+1/5+1/5+1/5 = 5/5 = 1 (task completed).
Hence 3*5 is used.
Golu said:
1 decade ago
Why we are calculating 2 days of work A?
Psyco said:
1 decade ago
1/5th work done in 3 days.
5/5th of work will be done in x days so,
1/5---3.
5/5---x.
x=3*5*5/5.
x=15.
5/5th of work will be done in x days so,
1/5---3.
5/5---x.
x=3*5*5/5.
x=15.
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