Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 7)
7.
A can do a piece of work in 4 hours; B and C together can do it in 3 hours, while A and C together can do it in 2 hours. How long will B alone take to do it?
Answer: Option
Explanation:
| A's 1 hour's work = | 1 | ; |
| 4 |
| (B + C)'s 1 hour's work = | 1 | ; |
| 3 |
| (A + C)'s 1 hour's work = | 1 | . |
| 2 |
| (A + B + C)'s 1 hour's work = |  |
1 | + | 1 |  |
= | 7 | . |
| 4 | 3 | 12 |
| B's 1 hour's work = | |
7 | - | 1 | |
= | 1 | . |
| 12 | 2 | 12 |
B alone will take 12 hours to do the work.
Discussion:
97 comments Page 10 of 10.
Elayabharathi said:
1 decade ago
No need of fraction, general understanding.
take lcm for 4,3,2 = 12 parts.
A =3p/d, BC=4p/d AC=6p/d.
so C alone do in (AC-A) 3p/d,
B(BC-C)=1p/d. So for 12 parts it ll take 12 DAYS for B do complete the same work.
question can be twisted like what is the ratio for A:B:C?
what will be the potential for cC?
ABOVE STEPS HAVE ALL THE ANSWERS YOU NEED!
take lcm for 4,3,2 = 12 parts.
A =3p/d, BC=4p/d AC=6p/d.
so C alone do in (AC-A) 3p/d,
B(BC-C)=1p/d. So for 12 parts it ll take 12 DAYS for B do complete the same work.
question can be twisted like what is the ratio for A:B:C?
what will be the potential for cC?
ABOVE STEPS HAVE ALL THE ANSWERS YOU NEED!
Mohit said:
1 decade ago
Why its taken 1/4 and 1/3 ? 4 and 3 why not?
Sai mounika said:
1 decade ago
It is easy to find out.
A+C = 1/2, A = 1/4.
(A+C) - A = 1/4 we got C = 1/4.
We know B+C = 1/3 then substitute C = 1/4 value here then we will get 1/12.
Hence B takes 12 hrs to complete the work.
A+C = 1/2, A = 1/4.
(A+C) - A = 1/4 we got C = 1/4.
We know B+C = 1/3 then substitute C = 1/4 value here then we will get 1/12.
Hence B takes 12 hrs to complete the work.
SIDHARTH said:
1 decade ago
A'S 1 hr work = 1/4.
(B's+ C's) 1hr work = 1/3.
Therefore, (A+B+C's)1 hr work = 1/4+1/3 = 7/12.
Therefore, B's 1hr work = 7/12 - 1/2 = 1/12.
Hence B takes 12 hrs to complete the work.
(B's+ C's) 1hr work = 1/3.
Therefore, (A+B+C's)1 hr work = 1/4+1/3 = 7/12.
Therefore, B's 1hr work = 7/12 - 1/2 = 1/12.
Hence B takes 12 hrs to complete the work.
Kartik said:
1 decade ago
a = 1/4 B+c = 1/3 a+c = 1/2 on subtracting b+c = 1/3 & a+c = 1/2 we got,
b-a = -1/6 and a = 1/4 (given) on putting these value we got b=12 is 1 day work so now total is 12 days.
It's Very Simple.
b-a = -1/6 and a = 1/4 (given) on putting these value we got b=12 is 1 day work so now total is 12 days.
It's Very Simple.
Amit Raj Modi said:
1 decade ago
I have one another method.
A can do total work in 4 hr.
B+C can do this in 3 hr.
A+C can do this in 2 hr.
Convert all of this in unit/hr.
Take LCM of 4, 3 and 2 which is 12 Unit (total unit of Work).
A can do work 12/4=3 unit/hr.
A+C can do work in 2 hr means A done 2hr*3unit=6unit. Now remaining work is 6 unit (hint:-12unit-6unit=6unit) which has done by C. So C can do 3 unit (hint:-6unit/2hr=3unit/hr) Work in 1 hr.
Now B+C can do work in 3 hr means C done 3hr*3Unit=9 Unit. Now remaining work is 3 unit (hint:-12unit-9unit=3 unit) which has done by B. So B can do 1 unit (hint:-3unit/3hr=1unit/hr) Work in 1 hr.
B takes 12 hr (hint:-12unit*1hr) to complete whole work.
You can do this method oraly. You need only some practice on this method.
A can do total work in 4 hr.
B+C can do this in 3 hr.
A+C can do this in 2 hr.
Convert all of this in unit/hr.
Take LCM of 4, 3 and 2 which is 12 Unit (total unit of Work).
A can do work 12/4=3 unit/hr.
A+C can do work in 2 hr means A done 2hr*3unit=6unit. Now remaining work is 6 unit (hint:-12unit-6unit=6unit) which has done by C. So C can do 3 unit (hint:-6unit/2hr=3unit/hr) Work in 1 hr.
Now B+C can do work in 3 hr means C done 3hr*3Unit=9 Unit. Now remaining work is 3 unit (hint:-12unit-9unit=3 unit) which has done by B. So B can do 1 unit (hint:-3unit/3hr=1unit/hr) Work in 1 hr.
B takes 12 hr (hint:-12unit*1hr) to complete whole work.
You can do this method oraly. You need only some practice on this method.
Rahul said:
1 decade ago
Hey there is no need to do so. Just.
Give as A's one day work is = 1/4.
(B+C) one day work = 1/3.
(A+C) one day work = 1/2.
As we know A = 1/4.
Then.
C = 1/2-1/4 = 1/4.
Then from given.
B = 1/3-1/4 = 1/12.
Give as A's one day work is = 1/4.
(B+C) one day work = 1/3.
(A+C) one day work = 1/2.
As we know A = 1/4.
Then.
C = 1/2-1/4 = 1/4.
Then from given.
B = 1/3-1/4 = 1/12.
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