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:
100 comments Page 5 of 10.
Gayathri said:
1 week ago
A = 1/4
B + C = 1/3 ----> eq(1)
A + C = 1/2 ----> eq(2)
Sub eq(1)-eq(2).
B + C - A - C = 1/3 - 1/2,
B - A = -1/6,
B = -1/6 + 1/4( where A=1/4).
B = 1/12.
Hence B alone takes 12 hours.
B + C = 1/3 ----> eq(1)
A + C = 1/2 ----> eq(2)
Sub eq(1)-eq(2).
B + C - A - C = 1/3 - 1/2,
B - A = -1/6,
B = -1/6 + 1/4( where A=1/4).
B = 1/12.
Hence B alone takes 12 hours.
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.
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.
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.
Moustafa Elhosiny said:
2 years ago
A's 1 hour = 1/4,
B+C 1 hour = 1/3,
A+C 1 hour = 1/2.
C = 1/2 - A
C = 1/2 - 1/4 = 1/4.
B+C = 1/3,
Then B = 1/3 -C.
B = 1/3 - 1/4 = 1/12.
So, B can do the work in 12 hours.
B+C 1 hour = 1/3,
A+C 1 hour = 1/2.
C = 1/2 - A
C = 1/2 - 1/4 = 1/4.
B+C = 1/3,
Then B = 1/3 -C.
B = 1/3 - 1/4 = 1/12.
So, B can do the work in 12 hours.
(8)
Haripriya said:
1 decade ago
a = 1/4;
b+c = 1/3;
a+c = 1/2.
Therefore find the c value first:- a+c = 1/2.
1/4+c = 1/2.
c = 1/4.
Now substitute in b+c = 1/3.
b+1/4 = 1/3.
b = 1/12 hence it takes 12 hours.
b+c = 1/3;
a+c = 1/2.
Therefore find the c value first:- a+c = 1/2.
1/4+c = 1/2.
c = 1/4.
Now substitute in b+c = 1/3.
b+1/4 = 1/3.
b = 1/12 hence it takes 12 hours.
Reshma said:
10 years ago
A = 1/4.
B + C = 1/3.
A + C = 1/2.
Subtract the above 2 equations we get,
B - A = 1/3 - 1/2,
B - A = -1/6,
B = -1/6 + 1/4,
B = 1/12,
So, B takes 12 hours to complete the work.
B + C = 1/3.
A + C = 1/2.
Subtract the above 2 equations we get,
B - A = 1/3 - 1/2,
B - A = -1/6,
B = -1/6 + 1/4,
B = 1/12,
So, B takes 12 hours to complete the work.
Komal pal said:
8 months ago
A = 4.
B + C = 3.
A + C = 2.
FIND THE LCM. 4,3,2=12
A = 3
B + C = 4.
A + C = 6.
Then;
A + C
3 + C = 6.
C = 6 - 3,
C = 3.
B + C = 4.
B + 3 = 4.
B = 4 - 3,
B = 1.
12/1=12
B + C = 3.
A + C = 2.
FIND THE LCM. 4,3,2=12
A = 3
B + C = 4.
A + C = 6.
Then;
A + C
3 + C = 6.
C = 6 - 3,
C = 3.
B + C = 4.
B + 3 = 4.
B = 4 - 3,
B = 1.
12/1=12
(14)
Abhimanyu said:
5 years ago
A = 4 B + C = 3 A + C = 2.
(B+C) - (A+C) + A = B(Making equation such that we will get value of B)
1/3 -1/2 + 1/4 = B.
B = 4 - 6 + 3/12(By taking kam) = 1/12.
B = 12.
(B+C) - (A+C) + A = B(Making equation such that we will get value of B)
1/3 -1/2 + 1/4 = B.
B = 4 - 6 + 3/12(By taking kam) = 1/12.
B = 12.
Bhanu said:
5 years ago
A = 1/4
A + C = 1/2 ---> eq1
B + C = 1/3 ---> eq2.
Substitute a = 1/4 in eq1.
C = 1/2-1/4
C = 1/4.
Sub C=1/4 in eq 2.
B+C=1/3.
B = 1/3-1/4.
= 1/12.
= 12 days.
A + C = 1/2 ---> eq1
B + C = 1/3 ---> eq2.
Substitute a = 1/4 in eq1.
C = 1/2-1/4
C = 1/4.
Sub C=1/4 in eq 2.
B+C=1/3.
B = 1/3-1/4.
= 1/12.
= 12 days.
(10)
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