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 4 of 10.
Shree said:
8 years ago
Clear and detailed explanation. Thank you all.
Bits said:
8 years ago
A in 4hrs.
B+C _ 3.
A+C _ 2.
Total work by taking lcm of 4,3,2 is 12units.
A in one day do = 12/4= 3.
A+C_ 6.
So C=3.
In the same way,
B+C= 12/3 > 4.
So B=1.
At last B =12/1=12. That's the answer!.
B+C _ 3.
A+C _ 2.
Total work by taking lcm of 4,3,2 is 12units.
A in one day do = 12/4= 3.
A+C_ 6.
So C=3.
In the same way,
B+C= 12/3 > 4.
So B=1.
At last B =12/1=12. That's the answer!.
(1)
Rohit said:
8 years ago
Guys!.
I simply subtracted the (A's) work - (B's+C's)work
so I got,
1/4-1/3=-1/12 for 1hour.
hence for b to do alone his work 12 hour.
I simply subtracted the (A's) work - (B's+C's)work
so I got,
1/4-1/3=-1/12 for 1hour.
hence for b to do alone his work 12 hour.
Bunny said:
8 years ago
Thank you so much @Himanshi Mishra.
I was looking for this LCM method. This is way too easy. Thanks.
I was looking for this LCM method. This is way too easy. Thanks.
Xyx said:
8 years ago
How it will 7/12-1/2=1/12?
(1)
Sam said:
8 years ago
You explained well @Akshay.
Himanshi mishra said:
8 years ago
@Ankita.
Follow this method.
Here total work is 12 hours as lcm of 2-4-3.
A does 3 work in 1 hour ND he finishes 12 work in four hours.
In the same way, abt A and C you know A does 3 work in 1 hour thus C also does 3 work in 1 hour so total work 6 in 1 hour thus 12 work in 2 hour is completed by A and C.
And now C does 3 work in 1 hour so b does 1 work in 1 hour and thus the both do 4 work in 1 hour and finishes in 3 hours.
As a result, B takes 1 hour to do 1 work so B Will take 12 hours to do 12 work.
Follow this method.
Here total work is 12 hours as lcm of 2-4-3.
A does 3 work in 1 hour ND he finishes 12 work in four hours.
In the same way, abt A and C you know A does 3 work in 1 hour thus C also does 3 work in 1 hour so total work 6 in 1 hour thus 12 work in 2 hour is completed by A and C.
And now C does 3 work in 1 hour so b does 1 work in 1 hour and thus the both do 4 work in 1 hour and finishes in 3 hours.
As a result, B takes 1 hour to do 1 work so B Will take 12 hours to do 12 work.
Ankita said:
9 years ago
How, 7/12 - 1/2 = 1/12?
Explain this step.
Explain this step.
Sandeep choudhary said:
9 years ago
A = 4.
B + C = 3.
A + C = 2.
Take LCM = 12.
ONE DAY WORK OF A = 12/4 = 3.
Similarly, B + C = 12/3 = 4------>1.
A+C = 12/2 = 6------> 2.
TOTAL ONE DAY WORK = 13.
PUT VALUE OF A in Eqn 2 and got the value of B then put in eqn 1 and got value of c=12.
B + C = 3.
A + C = 2.
Take LCM = 12.
ONE DAY WORK OF A = 12/4 = 3.
Similarly, B + C = 12/3 = 4------>1.
A+C = 12/2 = 6------> 2.
TOTAL ONE DAY WORK = 13.
PUT VALUE OF A in Eqn 2 and got the value of B then put in eqn 1 and got value of c=12.
Sandeep choudhary said:
9 years ago
A = 4.
B + C = 3.
A + C = 2.
Take LCM = 12.
ONE DAY WORK OF A = 12/4 = 3.
Similarly, B + C = 12/3 = 4------>1.
A+C = 12/2 = 6------> 2.
TOTAL ONE DAY WORK = 13.
PUT VALUE OF A in Eqn 2 and got the value of B then put in eqn 1 and got value of c=12.
B + C = 3.
A + C = 2.
Take LCM = 12.
ONE DAY WORK OF A = 12/4 = 3.
Similarly, B + C = 12/3 = 4------>1.
A+C = 12/2 = 6------> 2.
TOTAL ONE DAY WORK = 13.
PUT VALUE OF A in Eqn 2 and got the value of B then put in eqn 1 and got value of c=12.
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