Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 21)
21.
A takes twice as much time as B or thrice as much time as C to finish a piece of work. Working together, they can finish the work in 2 days. B can do the work alone in:
Answer: Option
Explanation:
| Suppose A, B and C take x, | x | and | x | days respectively to finish the work. |
| 2 | 3 |
| Then, |  |
1 | + | 2 | + | 3 |  |
= | 1 |
| x | x | x | 2 |
 |
6 | = | 1 |
| x | 2 |
x = 12.
So, B takes (12/2) = 6 days to finish the work.
Discussion:
68 comments Page 6 of 7.
Ritanjali natua said:
2 decades ago
1/x+2/x+3/x=6/x
Ravi said:
1 decade ago
Can anyone please explain me that how these x, x/2, x/3 become 1/x + 2/x + 3/x.
Here I don't get is we take 1 day's work of A as 1/x and after that it's taken 2/x + 3/x as B and C's 1 day work but actually after A's 1 day work B's & C's work should be taken as 1/x/2 and 1/x/3.
Which becomes x/2 and x/3 So finally it should look like 1/x + x/2 + x/3.
Here I don't get is we take 1 day's work of A as 1/x and after that it's taken 2/x + 3/x as B and C's 1 day work but actually after A's 1 day work B's & C's work should be taken as 1/x/2 and 1/x/3.
Which becomes x/2 and x/3 So finally it should look like 1/x + x/2 + x/3.
Khushwinder pal said:
1 decade ago
Another method.
Suppose C = X.
C = 2X then B = 3X, A = 6X.
Then B = 2X = 2*3 = 6 days.
If asked A = 6*3 = 18 days.
Suppose C = X.
C = 2X then B = 3X, A = 6X.
Then B = 2X = 2*3 = 6 days.
If asked A = 6*3 = 18 days.
Wangchuk Drukpa said:
1 decade ago
Let C takes x days to complete the work, then:
A, B, C.
3x, 3/2 x and x.
Their respective 1 day's work.
1/3x, 3/2x, 1/x now this is equal to 1/2 (as A+B+C takes 2 days to complete the work, thus their 1 day's work would be half).
Then we get x=4. Now 3/2 of 4 is 6.
A, B, C.
3x, 3/2 x and x.
Their respective 1 day's work.
1/3x, 3/2x, 1/x now this is equal to 1/2 (as A+B+C takes 2 days to complete the work, thus their 1 day's work would be half).
Then we get x=4. Now 3/2 of 4 is 6.
Kaviya said:
1 decade ago
How to comes the 1/x+2/x+3/x?
Rohini said:
1 decade ago
a=2b or a=3c.
=>b=a/2 , c=a/3.
Let us assume a=x.
Then,
a b c
x x/2 x/3
Therefore., (1/x + 2/x + 3/x) = 1/2.
6/x = 1/2.
x = 12.
B alone = x/2 = 12/2 = 6.
=>b=a/2 , c=a/3.
Let us assume a=x.
Then,
a b c
x x/2 x/3
Therefore., (1/x + 2/x + 3/x) = 1/2.
6/x = 1/2.
x = 12.
B alone = x/2 = 12/2 = 6.
Subhas said:
1 decade ago
A can complete 1 unit/day.
B can complete 2 unit/day.
C can complete 3 unit/day.
Total works complete together by all in 1 days = 6 unit/day.
So, they complete in two days = 6X2 = 12 units.
So B takes 12/2 = 6 days to complete.
B can complete 2 unit/day.
C can complete 3 unit/day.
Total works complete together by all in 1 days = 6 unit/day.
So, they complete in two days = 6X2 = 12 units.
So B takes 12/2 = 6 days to complete.
Brijesh said:
1 decade ago
Lets assume that A completes the work in 'x' days.
B completes the same amount of work in 'x/2' days because A takes twice the time than B.
C completes the same amount of work in 'x/3' days because A takes thrice the time than C.
Now the work completed by A in one day is '1/x'.
Work completed by B in one day is '2/x'
Work completed by C in one day is '3/x'
All three together can complete the work in '2' days as given in the problem. So the work done by all three together in one day is '1/2'.
Hence the equation: '(1/x + 2/x + 3/x) = 1/2'.
Evaluating the above equation gives the value 'x=12' which is the number of days taken by A to complete the work.
As we know that number of days taken by B complete the work is 'x/2', we substitute the 'x' value.
Hence the evaluation '12/2' where 12 is the value of 'x'.
HENCE THE TIME REQUIRED BY B TO COMPLETE THE WORK IS 6 DAYS.
B completes the same amount of work in 'x/2' days because A takes twice the time than B.
C completes the same amount of work in 'x/3' days because A takes thrice the time than C.
Now the work completed by A in one day is '1/x'.
Work completed by B in one day is '2/x'
Work completed by C in one day is '3/x'
All three together can complete the work in '2' days as given in the problem. So the work done by all three together in one day is '1/2'.
Hence the equation: '(1/x + 2/x + 3/x) = 1/2'.
Evaluating the above equation gives the value 'x=12' which is the number of days taken by A to complete the work.
As we know that number of days taken by B complete the work is 'x/2', we substitute the 'x' value.
Hence the evaluation '12/2' where 12 is the value of 'x'.
HENCE THE TIME REQUIRED BY B TO COMPLETE THE WORK IS 6 DAYS.
Krishman Varges said:
1 decade ago
This can be solved using physics. Force=Power/time. A, B and C does the same amount of work, hence, force is a constant. The power of three differs. Hence 1/t=f/p where f is a constant and t=2. 1/2=1/x+2/x+3/x.
Apeksha said:
1 decade ago
Why 12 is divided by 2 in last?
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