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 12 of 35.
Sagar said:
8 years ago
How to 300 come? Explain.
Ankit kain said:
8 years ago
Here is the perfect solution.
L.C.M- 60 (it is the lcm of 15 and 20 and here it is total work)
A's---------15 days|---EFFICIENCY-60÷15=4 (because, work= efficiency * time)
B's---------20 days|---EFFICIENCY-60÷20=3
combined efficiency of A and B =7.
work done by (A+B) in 4 days= 7 * 4=28(because work = efficiency * time).
hence ratio---------> 28/60=8/15.
L.C.M- 60 (it is the lcm of 15 and 20 and here it is total work)
A's---------15 days|---EFFICIENCY-60÷15=4 (because, work= efficiency * time)
B's---------20 days|---EFFICIENCY-60÷20=3
combined efficiency of A and B =7.
work done by (A+B) in 4 days= 7 * 4=28(because work = efficiency * time).
hence ratio---------> 28/60=8/15.
Rahul Manjhi said:
8 years ago
If A can do work in 15days then in 4days will be=4/15,
Similarly, if B can do work in 20days then 4days will be=4/20=1/5,
Therefore adding A and b together=4/15+1/5=7/15,
Now remaining work=1-7/15=8/15.
Similarly, if B can do work in 20days then 4days will be=4/20=1/5,
Therefore adding A and b together=4/15+1/5=7/15,
Now remaining work=1-7/15=8/15.
Yona said:
8 years ago
According to me,
=(4/15+4/20),
=(140/300),
=(7/15).
=(4/15+4/20),
=(140/300),
=(7/15).
Karthik said:
8 years ago
how 1-7/15 came? Please explain it clearly.
San said:
8 years ago
Here, 1/15+1/20= 20+15/300= 35/300 =7/60.
Aadesh said:
8 years ago
28/60=14/30=7/15 @Pooja.
Pooja said:
8 years ago
How, (7/60 * 4) = 7/15?
SUNDARA said:
8 years ago
A & B together requires 1/15+1/20=7/60 or 60/7days =8 4/7 days to complete the work.
After 4 days work, pending work is 8 4/7 -4=4 4/7days work.
= 4 4/7 divide by 8 4/7=32/7 divide 60/7=32/60=8/15 work pending.
After 4 days work, pending work is 8 4/7 -4=4 4/7days work.
= 4 4/7 divide by 8 4/7=32/7 divide 60/7=32/60=8/15 work pending.
Shubham said:
8 years ago
Thanks for the explanation @Swetha.
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