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 5 of 10.
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:
1 year 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:
10 years 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.
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.
Reshma said:
9 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.
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.
Piyus said:
1 decade ago
(b+c)of 1 hour-(a+c) of 1 hour = 1/3-1/2
=> b(1hr)-a(1hr)=(-1/6)
=> b(1hr)=1/4-1/6
=>b's 1hr work= 1/12
=>b ll take 12 hr to complete the work alone
=> b(1hr)-a(1hr)=(-1/6)
=> b(1hr)=1/4-1/6
=>b's 1hr work= 1/12
=>b ll take 12 hr to complete the work alone
Bhanu said:
4 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)
Swaathi said:
9 years ago
A = 1/4,
(B + C ) = 1/3,
(A + C ) = 1/2,
Subtract ( A + C ) and A,
We get C = 1/4 and then subtract (B + C ) and C,
We get B = 1/12,
Therefore 12 hours.
(B + C ) = 1/3,
(A + C ) = 1/2,
Subtract ( A + C ) and A,
We get C = 1/4 and then subtract (B + C ) and C,
We get B = 1/12,
Therefore 12 hours.
Varseyny said:
1 decade ago
A=1/4 (given)
(B+C)=1/3 (given)
(A+B+C)=(1/4+1/3) then take L.C.M
3+4/12=7/12
FIND FOR B
A+B+C=7/12
B=7/12-(A+C) given(A+C=1/2)
B=7/12-(1/2)=1/12
ANS:12
(B+C)=1/3 (given)
(A+B+C)=(1/4+1/3) then take L.C.M
3+4/12=7/12
FIND FOR B
A+B+C=7/12
B=7/12-(A+C) given(A+C=1/2)
B=7/12-(1/2)=1/12
ANS:12
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