Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 1)
1.
A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work that is left is :
Answer: Option
Explanation:
| A's 1 day's work = | 1 | ; |
| 15 |
| B's 1 day's work = | 1 | ; |
| 20 |
| (A + B)'s 1 day's work = |  |
1 | + | 1 |  |
= | 7 | . |
| 15 | 20 | 60 |
| (A + B)'s 4 day's work = | |
7 | x 4 | |
= | 7 | . |
| 60 | 15 |
| Therefore, Remaining work = | |
1 - | 7 | |
= | 8 | . |
| 15 | 15 |
Discussion:
344 comments Page 16 of 35.
Harry said:
9 years ago
I just came across an extremely easy way of solving this question. So felt like sharing it.
Work = LCM (15, 20) = 60 units.
A does 60/15 i.e. 4 units in a day, B does 60/20 i.e. 3 units in a day.
In 4 days work completed = (4 + 3) * 4 = 28 units.
Work left = Total work - work done by AB
= 60 - 28 = 32
So, Fraction of Work left = 32/60 = 8/15.
Work = LCM (15, 20) = 60 units.
A does 60/15 i.e. 4 units in a day, B does 60/20 i.e. 3 units in a day.
In 4 days work completed = (4 + 3) * 4 = 28 units.
Work left = Total work - work done by AB
= 60 - 28 = 32
So, Fraction of Work left = 32/60 = 8/15.
Deepa said:
9 years ago
@Swetha.
Thanks! Your explanation is very good and it is easy to understand.
Thanks! Your explanation is very good and it is easy to understand.
Rasim shaikh said:
9 years ago
Hello, friends!
Can anybody tell, how 1-7/15 get a plus? and I can't understand where the 1 come?
Please help me.
Can anybody tell, how 1-7/15 get a plus? and I can't understand where the 1 come?
Please help me.
Ashwini G C said:
9 years ago
Hi friends,
Happy to see you all discussing the problems and the solution given by each of them is awesome.
In fact, I could solve the problem by seeing this 'discussion forum'. I had all the doubts as others had and I used to get a solution for it. So, I thought of thanking you all.
Happy to see you all discussing the problems and the solution given by each of them is awesome.
In fact, I could solve the problem by seeing this 'discussion forum'. I had all the doubts as others had and I used to get a solution for it. So, I thought of thanking you all.
Sushant said:
9 years ago
How 7/60 come?
How to solve 1/15 + 1/20? Explain me.
How to solve 1/15 + 1/20? Explain me.
Anoof said:
9 years ago
60 divides 4 by 15 times that means 4 * 15 = 60.
Nanda said:
9 years ago
How you got 7/15?
GANESH said:
9 years ago
A do the work in 1 day is = 1/15.
B do the work in 1 day is = 1/20.
So LCM of 15, 20 is = 60.
Now,
A's work is 1/15 * 60 = 4.
B's work is 1/20 * 60 = 3.
Then (4 + 3/60) = 7/60.
7/60 is one day work of A+B.
We want 4 days work of A+B.
Then,
(4 * 7/60) = 28/60.
=> 7/15.
Now one day work is (1 - 7/15) = 15 - 7/15.
=> 8/15 is the answer.
B do the work in 1 day is = 1/20.
So LCM of 15, 20 is = 60.
Now,
A's work is 1/15 * 60 = 4.
B's work is 1/20 * 60 = 3.
Then (4 + 3/60) = 7/60.
7/60 is one day work of A+B.
We want 4 days work of A+B.
Then,
(4 * 7/60) = 28/60.
=> 7/15.
Now one day work is (1 - 7/15) = 15 - 7/15.
=> 8/15 is the answer.
Vikas said:
9 years ago
Can you explain how is 7/60 came?
Basivireddy said:
9 years ago
Hi guys, this is Basivireddy.
A can be work in 15 days = 1/15.
B Can be work in 30 days = 1/30.
1/15 + 1/30.
7/60 this is one day work.
We want 4 days work that's why it is 4*7/60 = 28/60 = 7/15.
Now one day work means they left one day so.
1-7/15 = 8/15, I hope so you understood, Thank you guys, have a great day.
A can be work in 15 days = 1/15.
B Can be work in 30 days = 1/30.
1/15 + 1/30.
7/60 this is one day work.
We want 4 days work that's why it is 4*7/60 = 28/60 = 7/15.
Now one day work means they left one day so.
1-7/15 = 8/15, I hope so you understood, Thank you guys, have a great day.
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