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 27 of 35.
Tabbu said:
7 years ago
Please explain this step 1-7/15.
Priya said:
7 years ago
A can do work in 15 days=1/15.
B can do work in 20 days=1/20.
both (A+B)=1/15+1/20=20+15/300=35/300=7/60.
(A+B)Work together in 4 days=7/60*4 in this 60 will be cancelled 4 table in 15.
Then; times=>7/15.
The remaining work will be(1-7/15).
=>15-7/15.
=>8/15.
B can do work in 20 days=1/20.
both (A+B)=1/15+1/20=20+15/300=35/300=7/60.
(A+B)Work together in 4 days=7/60*4 in this 60 will be cancelled 4 table in 15.
Then; times=>7/15.
The remaining work will be(1-7/15).
=>15-7/15.
=>8/15.
Raghavan said:
7 years ago
The LCM of 15 and 20 is 60 which means total work done=60. Then the efficiency of a & b are 4 & 3 respectively(one-day efficiency). Now if both work together their efficiencies must be added which is =7 and therefore 7*4=24.
Is the work was done by them for 4 days which means the leftover is 60-24=36.
Am I right?
Is the work was done by them for 4 days which means the leftover is 60-24=36.
Am I right?
Shurti said:
7 years ago
@Tabbu.
Here 1 means the whole part.
So subtract the work done from the whole work to get remaining work.
Here 1 means the whole part.
So subtract the work done from the whole work to get remaining work.
Sai Kumar reddy said:
7 years ago
The common Multiple for 15 and 20 is 5.
A's one day work =15*5=75 units,
B's one day work =20/5=4 units,
Both working together for 4 days=7*4=28 units.
A's one day work =15*5=75 units,
B's one day work =20/5=4 units,
Both working together for 4 days=7*4=28 units.
Esha said:
7 years ago
We consider work done in 15days=1/15 that means a piece of work done in 15 days. Similarly work done in 20 days = 1/20.
So the question is asked for 4 days which means 1/4. So we consider the remaining work to be done as 1.
So the question is asked for 4 days which means 1/4. So we consider the remaining work to be done as 1.
Subho said:
7 years ago
Kindly solve it in ratio method.
Raj said:
6 years ago
How 1-(7/15)=8/15? Please explain.
Manikkam said:
6 years ago
1- (7/5) = 8/5.
Because we consider the whole work as 1 then A and B together complete their job for 4 days is 7/5.
Then in the question, they are asking that the fraction of the remaining work so we subtract those values.
Because we consider the whole work as 1 then A and B together complete their job for 4 days is 7/5.
Then in the question, they are asking that the fraction of the remaining work so we subtract those values.
Meenu said:
6 years ago
Thanks for explaining @Swetha.
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