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 3 of 10.
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.
Jayanth babu said:
1 decade ago
Hi friends, in above problem
A=1/4----->(1)
B+C=1/3----->(2)
A+C=1/2------>(3)
now solving (2)
B+C=1/3
c=B-1/3--------->(4)
substitute (1) and (4) in (3)
then..
(1/4)+B-(1/3)=1/2
by solving this equation
B=1/12
Thus, B alone take 12hrs.
A=1/4----->(1)
B+C=1/3----->(2)
A+C=1/2------>(3)
now solving (2)
B+C=1/3
c=B-1/3--------->(4)
substitute (1) and (4) in (3)
then..
(1/4)+B-(1/3)=1/2
by solving this equation
B=1/12
Thus, B alone take 12hrs.
Dev said:
7 years ago
LET THE B CAN DO WORK IN X DAYS.
PART OF THE WORK IS DONE BY B+C = 1/3.
PART OF THE WORK IS DONE BY A+C = 1/2.
Now (B+C) - (A+C) = 1/3-1/2.
B-A = 1/3-1/2.
1/x-1/4 = 1/3-1/2.
1/x = 1/12 part of work.
So Work will be completed by B alone in 12 days.
PART OF THE WORK IS DONE BY B+C = 1/3.
PART OF THE WORK IS DONE BY A+C = 1/2.
Now (B+C) - (A+C) = 1/3-1/2.
B-A = 1/3-1/2.
1/x-1/4 = 1/3-1/2.
1/x = 1/12 part of work.
So Work will be completed by B alone in 12 days.
Decoder said:
1 decade ago
What is wrong with this approach :
C 's 1 hour work=(A+C)'s 1 hour work -A 's 1 hour work=1/2
then B's i hour work = (B+C)'s 1 hour work-C's 1 hour work =1/6
But the answer as mentioned with another approach is 1/12
Can anybody explain ?
C 's 1 hour work=(A+C)'s 1 hour work -A 's 1 hour work=1/2
then B's i hour work = (B+C)'s 1 hour work-C's 1 hour work =1/6
But the answer as mentioned with another approach is 1/12
Can anybody explain ?
Hindu said:
1 decade ago
Take the given data as 2 equations as follows
A=1\4 ,B+C=1\3--eq1 and A+C=1\2---eq2
put A=1\4 in eq2
1\4+C=1\2
C=1\2-1\4 we get
C=1\4
put C=1\4 in eq1
B+1\4=1\3
B=1\3-1\4 we get
B=1\12
Therefore B alone take 12hours to do a work
A=1\4 ,B+C=1\3--eq1 and A+C=1\2---eq2
put A=1\4 in eq2
1\4+C=1\2
C=1\2-1\4 we get
C=1\4
put C=1\4 in eq1
B+1\4=1\3
B=1\3-1\4 we get
B=1\12
Therefore B alone take 12hours to do a work
Kumar Pawar said:
1 year ago
A = 1/4 ---> (1)
B + C = 1/3 ---->(2)
A + C = 1/2---->(3)
Put Equation in (1)in (3)
A + C = 1/2.
1/4 + C = 1/2,
C = 1/2 - 1/4 = 1/4.
C = 1/4.
Put C in equation (2).
B + 1/4 = 1/3
B = 1/3 - 1/4
B = 1/12 Days.
So, the Answer is 12 days.
B + C = 1/3 ---->(2)
A + C = 1/2---->(3)
Put Equation in (1)in (3)
A + C = 1/2.
1/4 + C = 1/2,
C = 1/2 - 1/4 = 1/4.
C = 1/4.
Put C in equation (2).
B + 1/4 = 1/3
B = 1/3 - 1/4
B = 1/12 Days.
So, the Answer is 12 days.
(14)
Hemaharshini said:
2 years ago
A = 1/4 ---(1)
B + C = 1/3 ----(2)
A + C = 1/2----(3)
=>Sub (1) in (3)
1/4 + C =1/2
C=1/4 => one day work of C---- (4)
=> Now sub (4) in (2) to find b's one day's work.
B + 1/4 = 1/3.
B = 1/12
B = 12 hours.
B + C = 1/3 ----(2)
A + C = 1/2----(3)
=>Sub (1) in (3)
1/4 + C =1/2
C=1/4 => one day work of C---- (4)
=> Now sub (4) in (2) to find b's one day's work.
B + 1/4 = 1/3.
B = 1/12
B = 12 hours.
(40)
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.
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.
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