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.
Sri said:
9 years ago
Please give the short trick 'with efficiency' then the sum will be solved very quickly.
Mani said:
9 years ago
How to find the solution of this question? Please solve this by easy method.
Israel said:
9 years ago
A can do the work in 15days, hence he does 1/15 of the work in a day.
B can do the work in 20days, hence he does 1/20 of the work in a day.
Working together, they will do (1/15)+(1/20)= 7/60 of the total work.
In 4 days, they would have done 4 * (7/60) = 7/15 of the total work (E.g they have built 7 houses out of the 15 houses they were to build).
Hence, they need to build 8 more houses to complete their work. That is how we get 8/15 as the FRACTION of work remaining.
I hope that was comprehensive enough.
B can do the work in 20days, hence he does 1/20 of the work in a day.
Working together, they will do (1/15)+(1/20)= 7/60 of the total work.
In 4 days, they would have done 4 * (7/60) = 7/15 of the total work (E.g they have built 7 houses out of the 15 houses they were to build).
Hence, they need to build 8 more houses to complete their work. That is how we get 8/15 as the FRACTION of work remaining.
I hope that was comprehensive enough.
Koteswararao chimmili said:
9 years ago
A's 1 day's work = 1/15;
B's 1 day's work = 1/20;
(A + B)'s 1 day's work = (1/15 + 1/20)
LCM = 60
5 | 15 , 20
__________
3 , 4
= 5*3*4 = 60
(A + B)'s 1 day's work = (4/60 + 3/60) ( 4/60 = 1/15 AND 3/60 =1/20 )
= 7/60
(A + B)'s 4 day's work = 7/60*4
= 28/60
= 7/15 .
Therefore, Remaining work = (1 - 7/15)
= (15-7)/15
= 8/15.
B's 1 day's work = 1/20;
(A + B)'s 1 day's work = (1/15 + 1/20)
LCM = 60
5 | 15 , 20
__________
3 , 4
= 5*3*4 = 60
(A + B)'s 1 day's work = (4/60 + 3/60) ( 4/60 = 1/15 AND 3/60 =1/20 )
= 7/60
(A + B)'s 4 day's work = 7/60*4
= 28/60
= 7/15 .
Therefore, Remaining work = (1 - 7/15)
= (15-7)/15
= 8/15.
Vikrant said:
9 years ago
Simple that how get 7/60. 15 + 20/15 * 20 = 35 / 300.
So, 7 * 5 = 35 & 60 * 5 = 300. Thats it!
So, 7 * 5 = 35 & 60 * 5 = 300. Thats it!
Innareddy chilakala said:
9 years ago
(15 * 20)/15 + 20 = 60/7.
Work done in 4 days (7/60) * 4 = 7/15,
Remaining work is 1 - 7/15 = 8/15.
Work done in 4 days (7/60) * 4 = 7/15,
Remaining work is 1 - 7/15 = 8/15.
Vivek said:
9 years ago
How 7/60 came?
Ramkali said:
9 years ago
Why do we want to calculate 1-7/15?
Sunita Devi said:
9 years ago
Why this answer is not sufficient at this term : (7/15)?
Why do this term (1-8/15)?
Why do this term (1-8/15)?
Ammu said:
8 years ago
A's 1 day work = 1/15.
B's 1 day work = 1/20.
Together for 1 day=(1/15+1/20),
=(4+3)/60,
=7/60.
together for 4 days=(7/60) * 4,
= 7/15.
If total work is 1.
Then the rest is = 1 - 7/15,
= 8/15.
B's 1 day work = 1/20.
Together for 1 day=(1/15+1/20),
=(4+3)/60,
=7/60.
together for 4 days=(7/60) * 4,
= 7/15.
If total work is 1.
Then the rest is = 1 - 7/15,
= 8/15.
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