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?
8 hours
10 hours
12 hours
24 hours
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

Therefore B alone will take 12 hours to do the work.

Discussion:
89 comments Page 1 of 9.

Vijay said:   1 month ago
(B+C)-(A+C) = (B-A).
(B-A)+(A) = B.
1/3-1/2+1/4= 4/12 - 6/12 + 3/12 = 1/12.
= 12 hrs.
(3)

Hemaharshini said:   11 months 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.
(30)

Jagadish Behera said:   2 years ago
DATA GIVEN:
A=4hrs
B+C=3hrs
A+C=2hrs.
B=?
Ans: Total work =12

A = 3work
B+C = 4work
A+C = 6work
A+C = 6.

3 + C = 6
C=6-3 = 3 WORK.

B+C=4
B=4-3=1

So, that B alone whole work in 12/1 = 12 hrs.
(43)

Dhananjay said:   2 years ago
A 1 hours work = 1/4 ----> (i)
B+C 1 hors work = 1/3 ----> (ii)
A+C 1 hour work = 1/2 ----> (iii).

By subtracting from (iii) to (ii) we get A-B = 1/6.
Now in place of A put the value of A = 1/4.
1/4-B = 1/6,
1/4-1/6 = B.
1/12 IS B'S 1 Hour's work.
B will take 12 hours.
(7)

Spoorti said:   3 years ago
Thank you @Bhanu.
(3)

Bhanu said:   3 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.
(9)

Arumugam said:   3 years ago
A = 1/4,
A+b = 1/3.
B = 1/3-1/4 = 1/12.
And = 12.
(5)

Logesh said:   3 years ago
Simply, subs A's value in Eqn 1:
A + C= 1/2
C = 1/2-1/4
C = 1/4

Sub C's VALUE IN B+C = 1/3;
B = 1/3-1/4
B = 1/12 , we got it.
(2)

Namrata Gujar said:   3 years ago
A = 4
B+c = 3
A+c = 2.

Lcm office 4,3,2 is 12.
A+c = 2,
4+c = 2,
C = 4-2,
C = 2.

B+c = 3,
B+2 = 3,
B = 1.

Total work 12.
12*1 = 12.
(13)

Aman Jadhao said:   3 years ago
Hi;

a=4h
B+c=3h
A+c=2h
B=?.

A b+c. A+c
4. 3 2

Take LCM of
Lcm=12
After LCM value is
3. 4. 6.

Adding the value we get
A + c = 2
C = 1.

Then solve
B+c =4,
B=3.

Simply multiple with LCM values of b&c
3 * 4 = 12 hours.
(3)


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