Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 16)
16.
X and Y can do a piece of work in 20 days and 12 days respectively. X started the work alone and then after 4 days Y joined him till the completion of the work. How long did the work last?
Answer: Option
Explanation:
| Work done by X in 4 days = |  |
1 | x 4 |  |
= | 1 | . |
| 20 | 5 |
| Remaining work = | |
1 - | 1 | |
= | 4 | . |
| 5 | 5 |
| (X + Y)'s 1 day's work = | |
1 | + | 1 | |
= | 8 | = | 2 | . |
| 20 | 12 | 60 | 15 |
| Now, | 2 | work is done by X and Y in 1 day. |
| 15 |
| So, | 4 | work will be done by X and Y in | |
15 | x | 4 | |
= 6 days. |
| 5 | 2 | 5 |
Hence, total time taken = (6 + 4) days = 10 days.
Discussion:
68 comments Page 7 of 7.
Aakash said:
1 decade ago
x+4/20+x/12 = 1.
3(x+4)+5(x)/60 = 1.
3x+12+5x = 60.
8x+12 = 60.
8x = 60-12.
8x = 48.
x = 6.
i.e., x+4 = 6+4.
10 days.
3(x+4)+5(x)/60 = 1.
3x+12+5x = 60.
8x+12 = 60.
8x = 60-12.
8x = 48.
x = 6.
i.e., x+4 = 6+4.
10 days.
Deepak Patgar said:
1 decade ago
Chocolate method:
LCM of 20 and 12 is 60. there are 60 chocolates and.
A requires 20 days to eat 60 chocolates. He eats 3 chocolates per day.
B requires 12 days to eat 60 chocolates. He eats 5 chocolates per day.
For the first 4 days A alone eats the chocolates. total number of chocolates eaten up by A in 4 days is 12.
Remaining chocolates are (60-12) = 48.
A and B together eats 8 chocolates per day.
So to eat 48 chocolates they will need 48/8 = 6 days.
Total number of days = 4+6 = 10.
LCM of 20 and 12 is 60. there are 60 chocolates and.
A requires 20 days to eat 60 chocolates. He eats 3 chocolates per day.
B requires 12 days to eat 60 chocolates. He eats 5 chocolates per day.
For the first 4 days A alone eats the chocolates. total number of chocolates eaten up by A in 4 days is 12.
Remaining chocolates are (60-12) = 48.
A and B together eats 8 chocolates per day.
So to eat 48 chocolates they will need 48/8 = 6 days.
Total number of days = 4+6 = 10.
Prasana said:
1 decade ago
Why we are adding plus 4?
Chandra said:
1 decade ago
Because 4 days work done by x. In question they asked total number of days.
Chandra said:
1 decade ago
Because 4 days work done by x. In question they asked total number of days.
Ajith said:
1 decade ago
I this way also it can be thought about:
Assume total days for completion = N.
X 's 1 day's effort = 1/20.
Y's 1 day's effort = 1/12.
(1/20)*N = (1/12)*(N-4)----[i.e, X's N days work = Y's (N-4) days work].
By solving, N = 10 days.
Assume total days for completion = N.
X 's 1 day's effort = 1/20.
Y's 1 day's effort = 1/12.
(1/20)*N = (1/12)*(N-4)----[i.e, X's N days work = Y's (N-4) days work].
By solving, N = 10 days.
Jyoti said:
1 decade ago
How y=1 /12 please explain?
Kumutha said:
1 decade ago
Please discuss clearly.
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