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 17 of 35.
Mukesh gautam said:
10 years ago
Simple method:
A-15.
B-20.
LCM is 60.
60/15 = 4.
60/20 = 3.
Total work 60 an total unit work done by a and b is 7.
In q4 day work are done than total 4 day work is 7x4 = 28.
Remaining work 60-28 = 32.
Fraction of remaining work is 32/60 = 8/15. Solution are done in only 20 sec. This method is very simple and less time consuming.
A-15.
B-20.
LCM is 60.
60/15 = 4.
60/20 = 3.
Total work 60 an total unit work done by a and b is 7.
In q4 day work are done than total 4 day work is 7x4 = 28.
Remaining work 60-28 = 32.
Fraction of remaining work is 32/60 = 8/15. Solution are done in only 20 sec. This method is very simple and less time consuming.
Priya said:
10 years ago
Can you explain how this 7/15 came?
Birander yadav said:
10 years ago
1/15+1/20 = 7/60*2 = 7/15.
Total work day = 1-7/15 = 8/15.
Total work day = 1-7/15 = 8/15.
Shruti said:
10 years ago
How 60 came?
Debasis Das said:
10 years ago
A's 1 day work = 1/15.
B's 1 day work = 1/20.
Hence, A+B 1 day work = (1/15+1/20) = 7/60.
So, A+B 4 day work = (7/60*4) = 7/15.
Then, remaining work = 1-7/15 = 8/15.
B's 1 day work = 1/20.
Hence, A+B 1 day work = (1/15+1/20) = 7/60.
So, A+B 4 day work = (7/60*4) = 7/15.
Then, remaining work = 1-7/15 = 8/15.
ASHLYMOL SAJU said:
10 years ago
A B A+B.
15 20 4.
Work = Efficiency/Time.
Work = LCM of A B A+B.
W = 60.
A B A+B = 4 3 15.
Total = 7/15.
Remaining = 8/15.
15 20 4.
Work = Efficiency/Time.
Work = LCM of A B A+B.
W = 60.
A B A+B = 4 3 15.
Total = 7/15.
Remaining = 8/15.
Jinto said:
10 years ago
(A+B) 's 1 day's work = 7/60.
So (A+B) can finish the work in 60/7 day.
(A+B) 's 4 day's work = 7/15.
So remaining work = (60/7) - (7/15).
Is this correct? Why remaining work = (1-7/15), from where 1 came?
So (A+B) can finish the work in 60/7 day.
(A+B) 's 4 day's work = 7/15.
So remaining work = (60/7) - (7/15).
Is this correct? Why remaining work = (1-7/15), from where 1 came?
LOURDHU RANI said:
10 years ago
How came 1-7/15 step, I don't understand?
BIKASH SAHOO said:
10 years ago
(1-7/15) this process I can not understood.
Ashwini said:
10 years ago
Its very simple 1/1-7/15.
LCM between 1 and 15 is 15.
So = (1/1)*(15/15) - (7/15)*(1/1) {Make both the denominator as 15 i.e LCM}.
= 15/15 - 7/15.
= (15-7)/15 = 8/15.
Hope understood!
LCM between 1 and 15 is 15.
So = (1/1)*(15/15) - (7/15)*(1/1) {Make both the denominator as 15 i.e LCM}.
= 15/15 - 7/15.
= (15-7)/15 = 8/15.
Hope understood!
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