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 30 of 35.
Joel said:
4 years ago
Lets take total work is = 1.
In 15 days A will complete the work;
In one day he comlete 1/15 part of work,
Similarly B comletes 1/20 work in one day.
Hence A and B both completes 1/15 + 1/20 work in one day
1/15+1/20 = 7/60.
A and B's one day work,
thier 4 days work = 4 * (7/60) = 28/60 = >7/15,
Now total work is 1,
They completed 7/15 work in 4 days,
Now remaining work is1-7/15 = 8/15.
In 15 days A will complete the work;
In one day he comlete 1/15 part of work,
Similarly B comletes 1/20 work in one day.
Hence A and B both completes 1/15 + 1/20 work in one day
1/15+1/20 = 7/60.
A and B's one day work,
thier 4 days work = 4 * (7/60) = 28/60 = >7/15,
Now total work is 1,
They completed 7/15 work in 4 days,
Now remaining work is1-7/15 = 8/15.
Ashutosh Sharma said:
4 years ago
A takes 15 days & B takes 20 days.
L.C.M. of 15 and 20 is 60 ( Total work)
Then
A works in a day 60÷15 = 4 &,
B works in a day 60÷20 = 3.
When both works together;
A+B works in a day (4+3) = 7.
They works for 4 days then 7*4 = 28,
Remaining work is 60 - 28 = 32,
The fraction of left work is 32/60 = 8/15.
L.C.M. of 15 and 20 is 60 ( Total work)
Then
A works in a day 60÷15 = 4 &,
B works in a day 60÷20 = 3.
When both works together;
A+B works in a day (4+3) = 7.
They works for 4 days then 7*4 = 28,
Remaining work is 60 - 28 = 32,
The fraction of left work is 32/60 = 8/15.
Jigme wangchuk said:
4 years ago
Simple method.
A = 15 days,
B = 20 days,
No days of work together (A+B) = 4 days,
Fraction of work = 4* sum/product.
= 4*(15+20/15*20) =140/300 simplify = 7/15.
Now, remaining fraction of work = 1-7/15
= 8/15.
A = 15 days,
B = 20 days,
No days of work together (A+B) = 4 days,
Fraction of work = 4* sum/product.
= 4*(15+20/15*20) =140/300 simplify = 7/15.
Now, remaining fraction of work = 1-7/15
= 8/15.
SkiGi said:
4 years ago
Why 7/60? I don't understand, please someone explain.
Yusuf said:
4 years ago
A+b 1 days work =7/60.
(2)
Abishek Thapa said:
4 years ago
LCM of A's and B's:
A-15
B-20.
LCM is 60 (It is also total Work) and Efficiency is TOTAL WORK/ TIME i.e.
60/15 = 4 <<<A's 1 day Efficiency
60/20 = 3 <<<B's 1 day Efficiency.
Combining both 1-day Efficiency then we get 4+3=7 (It means A and B can do 7 units in 1 day)
According to the question:
if they have 7 unit Efficiency they work for 4 days then we get:
7 x 4 and divide by total work (60).
7 x 4/60= 7/15 << it is the part of work they will finish in 4 days.
But the question was asked about how much fraction is left then simply we know that total work is 1 then subtract total work 1-7/15.
We get 8/15 that is the answer.
A-15
B-20.
LCM is 60 (It is also total Work) and Efficiency is TOTAL WORK/ TIME i.e.
60/15 = 4 <<<A's 1 day Efficiency
60/20 = 3 <<<B's 1 day Efficiency.
Combining both 1-day Efficiency then we get 4+3=7 (It means A and B can do 7 units in 1 day)
According to the question:
if they have 7 unit Efficiency they work for 4 days then we get:
7 x 4 and divide by total work (60).
7 x 4/60= 7/15 << it is the part of work they will finish in 4 days.
But the question was asked about how much fraction is left then simply we know that total work is 1 then subtract total work 1-7/15.
We get 8/15 that is the answer.
(3)
Md Afif said:
4 years ago
How 1-7/15? Explain.
(3)
Jyothi said:
4 years ago
I am not getting. How 1-7/15? Explain, please.
(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)
AKT said:
3 years ago
Thanks everyone for explaining the answer.
(3)
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