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 9 of 10.
Abhin said:
10 years ago
By the way why we are reciprocating 1/12 into 12?
TEJASHWINI said:
1 decade ago
A =1/4 then substitute in A+C = 1/2 we get 1/4+C = 1/2.
C = 1/2-1/4 = 1/4.
Substitute this value of C in B+C = 1/3 we get B+1/4 = 1/3.
B = 1/3-1/4 = 1/12.
Answer is 12 hours.
C = 1/2-1/4 = 1/4.
Substitute this value of C in B+C = 1/3 we get B+1/4 = 1/3.
B = 1/3-1/4 = 1/12.
Answer is 12 hours.
SAI said:
1 decade ago
B = A+ (B+C) - (A+C) = 1/4 + 1/3 -1/2 = 1/12.
B = 12.
B = 12.
Harish said:
1 decade ago
A's 1 hour's work = 1/4.
(A + C) 's 1 hour's work = 1/2.
1/4 + C = 1/2.
C = 1/4.
(B + C) 's 1 hour's work = 1/3.
B + 1/4 = 1/3.
B = 1/12 (B's 1 hour work).
So B = 12 days.
(A + C) 's 1 hour's work = 1/2.
1/4 + C = 1/2.
C = 1/4.
(B + C) 's 1 hour's work = 1/3.
B + 1/4 = 1/3.
B = 1/12 (B's 1 hour work).
So B = 12 days.
Saleem said:
1 decade ago
Hi.
A = 1/4....(1).
B+C = 1/3....(2).
A+C = 1/2....(3).
Now solve equation (1) & (3).
1/4+C = 1/2.
C = 1/4....(4).
Put C value in equation (2).
B+1/4 = 1/3.
B = 1/3-1/4.
B = 1/12 that's the answer.
A = 1/4....(1).
B+C = 1/3....(2).
A+C = 1/2....(3).
Now solve equation (1) & (3).
1/4+C = 1/2.
C = 1/4....(4).
Put C value in equation (2).
B+1/4 = 1/3.
B = 1/3-1/4.
B = 1/12 that's the answer.
Rucha said:
1 decade ago
How the answer for a+b+c = 7/12?
Raj said:
1 decade ago
Hi friends, my explanation.
A=1/4.
B and C Compain to work in 3 hours.
so B+C=1/3.
A and C compain to work in 2 hours.
so, A+C=1/2.
Put a=1/4.
1/4+c=1/2.
c=1/4.
B+C=1/3.
1/4+C=1\3.
C=12.
A=1/4.
B and C Compain to work in 3 hours.
so B+C=1/3.
A and C compain to work in 2 hours.
so, A+C=1/2.
Put a=1/4.
1/4+c=1/2.
c=1/4.
B+C=1/3.
1/4+C=1\3.
C=12.
Raj said:
1 decade ago
Hi friends, my explanation.
A=1/4.
B and C Compain to work in 3 hours.
so B+C=1/3.
A and C compain to work in 2 hours.
so, A+C=1/2.
Put a=1/4.
1/4+c=1/2.
c=1/4.
B+C=1/3.
1/4+C=1\3.
C=12.
A=1/4.
B and C Compain to work in 3 hours.
so B+C=1/3.
A and C compain to work in 2 hours.
so, A+C=1/2.
Put a=1/4.
1/4+c=1/2.
c=1/4.
B+C=1/3.
1/4+C=1\3.
C=12.
Paci said:
1 decade ago
How can calculate 7/12 - 1/2 = 1/12?
Yogesh H B said:
1 decade ago
A's 1hr work= 1/4......(1).
B+C=1/3.....(2).
A+C=1/2.......(3).
Solve eqn 1 and 3, we get,
C=1/4.
Put value of C in eqn (2), we get,
B=1/12.
So, B can finish a work in 12 days.
B+C=1/3.....(2).
A+C=1/2.......(3).
Solve eqn 1 and 3, we get,
C=1/4.
Put value of C in eqn (2), we get,
B=1/12.
So, B can finish a work in 12 days.
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