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:
347 comments Page 5 of 35.
Sankalp said:
3 years ago
Please explain, why the remaining work is 1.
(60)
Vinitha said:
3 years ago
@all
(1/15+1/20) =7/60.
Solution:
We have to use the mixed fraction method in a simple way using cross multiplication so it becomes (15+20)/300.
The reason for the 300 came we use the denominator direct multiplication (15*20=300)
Then 15+20 = 35,
Divide:35/300.
It becomes 7/60.
(1/15+1/20) =7/60.
Solution:
We have to use the mixed fraction method in a simple way using cross multiplication so it becomes (15+20)/300.
The reason for the 300 came we use the denominator direct multiplication (15*20=300)
Then 15+20 = 35,
Divide:35/300.
It becomes 7/60.
(38)
Radhika said:
3 years ago
@All.
As 1 is the whole work, so when we subtract 7/15 from 1.
Then,
LCM of 1 and 15 will be 15 ( in 1 the denominator will be 1 ).
So, 15-7/15 is 8/15.
As 1 is the whole work, so when we subtract 7/15 from 1.
Then,
LCM of 1 and 15 will be 15 ( in 1 the denominator will be 1 ).
So, 15-7/15 is 8/15.
(18)
Ayansh said:
3 years ago
How (1/15+1/20) = 7/60? Please explain me.
(37)
Dibyanshu said:
3 years ago
A - 15 days.
B - 20 days.
LCM of 15 & 20 is 60 (The total work is 60 also).
So,
The Efficiency of one day's work is 60/15 = 4 and 60/20 = 3.
Then, both A & B can complete the work in one day is 4+3=7.
They worked for 4 days, so 7x4=28
Work completed in 4days by both A+B=28.
Then, rest work = Total work - Completed work
Rest work = 60-28=32.
32/60 = 8/15
The answer is = 8/15.
B - 20 days.
LCM of 15 & 20 is 60 (The total work is 60 also).
So,
The Efficiency of one day's work is 60/15 = 4 and 60/20 = 3.
Then, both A & B can complete the work in one day is 4+3=7.
They worked for 4 days, so 7x4=28
Work completed in 4days by both A+B=28.
Then, rest work = Total work - Completed work
Rest work = 60-28=32.
32/60 = 8/15
The answer is = 8/15.
(233)
VisHnu RaM said:
4 years ago
Thank you for giving the clear explanation @Swetha.
And 60 will come, No of days LCM
15 days to 15 * 4 = 60.
20 days to 20 * 3 = 60.
So, the LCM is 60.
And 60 will come, No of days LCM
15 days to 15 * 4 = 60.
20 days to 20 * 3 = 60.
So, the LCM is 60.
(13)
Swetha said:
4 years ago
First of all, thank you to explain the method.
I have a doubt that how we know to take (i.e Total work = 60)?
Anyone, please help me to get it.
I have a doubt that how we know to take (i.e Total work = 60)?
Anyone, please help me to get it.
(6)
AKT said:
4 years ago
Thanks everyone for explaining the answer.
(3)
Ankita said:
4 years ago
@Jyoti.
It's 1 -7/15 as it is asking how much work is left. Which means 1 is the total amount of work, and 7/15 is the amount of work completed.
So, to get the remaining work we hv to subtract the work done by the whole work. Which is
1-7/15.
= 15/15 - 7/15.
= 15-7/15.
= 8/15.
Hope it helps.
It's 1 -7/15 as it is asking how much work is left. Which means 1 is the total amount of work, and 7/15 is the amount of work completed.
So, to get the remaining work we hv to subtract the work done by the whole work. Which is
1-7/15.
= 15/15 - 7/15.
= 15-7/15.
= 8/15.
Hope it helps.
(15)
Jyothi said:
4 years ago
I am not getting. How 1-7/15? Explain, please.
(3)
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