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 18 of 35.
Mohsin said:
10 years ago
How (7/60*4) = 7/15?
Bhargav said:
10 years ago
I don't understand why we take 1-7/15?
RANGADHAR said:
10 years ago
If the total work is taking the LCM of 15 & 20.
Then it will be 60.
A = 15 days.
B = 20 days.
LCM = 60 work.
Then A do in one day = 60/15 = 4 work.
B = 60/20 = 3 work.
In one day they work = {4+3} work.
In 4 days = 7*4 = 28 works.
Remaining = 60-28 = 32 work.
Then 32/60 = 8/15.
Then it will be 60.
A = 15 days.
B = 20 days.
LCM = 60 work.
Then A do in one day = 60/15 = 4 work.
B = 60/20 = 3 work.
In one day they work = {4+3} work.
In 4 days = 7*4 = 28 works.
Remaining = 60-28 = 32 work.
Then 32/60 = 8/15.
Dinesh said:
10 years ago
This problem ok I can understand but some other problems I can't understand my dear friends.
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!
BIKASH SAHOO said:
10 years ago
(1-7/15) this process I can not understood.
LOURDHU RANI said:
10 years ago
How came 1-7/15 step, I don't understand?
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?
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.
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.
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