Aptitude - Time and Work - Discussion

Discussion Forum : Time and Work - General Questions (Q.No. 21)
21.
A takes twice as much time as B or thrice as much time as C to finish a piece of work. Working together, they can finish the work in 2 days. B can do the work alone in:
4 days
6 days
8 days
12 days
Explanation:

 Suppose A, B and C take x, x and x days respectively to finish the work. 2 3

 Then, 1 + 2 + 3 = 1 x x x 2

 6 = 1 x 2

x = 12.

So, B takes (12/2) = 6 days to finish the work.

Discussion:
66 comments Page 1 of 7.

Karthick M said:   1 year ago
To simple method is:
A = 2B or A=3B
(A+B)'s 1day work = 1/2=(2B+B)'s 1day work
1/2 = 3B's 1-day work
ie, B's 1 day work = 1/6
So, B's whole work done is in 6 days.
(4)

Mahendra said:   2 years ago
Assume total work iso no of chairs from the give no of chair made per one day as per efficiency
A : B : C = 1 : 2 : 3.
So total chairs is 6 in one day.
Total days they together : 2 days.
So, total works = 6 * 2 = 12.
B alone can take = 12/2 = 6 days.
(20)

Banjeet said:   3 years ago
A : B : C = 6 : 3 : 2,
11*2= 22 work,
So, B doing = (3/11) * 22 = 6 days.
(10)

Tyson said:   3 years ago
As the question says,

The time taken by A is twice that of B and thrice that of C, so
This means that;
Efficiency,
A=2*B=3*C

Efficiency is inversely proportional to the time taken to complete a task.

Time ratio
A/B=2/1,
A/C=3/1

So, the Efficiency ratio

A/B=1/2,
A/C=1/3
=>A/B/C=1/2/3.
A:B:C=1:2:3.

So in terms of RATIO,

Let 1-day work of A,B, C be 1unit, 2unit, 3unit.
i.e. work for A: 1 Day= 1 U---->eqn 1
work for B: 1 Day= 2 U----> eqn 2
Work for C: 1 Day= 3 U----eqn 3
Work for A+B+C: 1 Day= 6 U.
2 Day=12U----eqn iv
[Total work(12U) completes in Time =2days(given)
i.e.Total Works time taken by A+B+C, Time =2days]
Comparing (eqn ii & iv) find B can do the work alone
Work for B: 1 Day = 2 U ----> eqn 2
work for B: 3x2 Day = 6x2 U.
6 DAYS = 12 U.

B alone do the work in time = 6 days.
(1)

Abhishek said:   3 years ago
Let's assume.
C takes 4 days to do X work.
B takes 6 days for the same X work.
A takes 12 days for the same X work.

so, efficiency
A = 1/12.
B = 1/6.
c = 1/4.

So, as they all together takes 2 days to work,

x/(1/12)+(1/6)+(1/4) = 2
From that, we got X ( total work ) = 1
So time taken alone by;
B = 1/(1/) = 6 days.

Subhasish baul said:   4 years ago
A - 12.
B - 6.
C - 4.

Work as satisfied to take together 2day finished.
Efficiency A 1 B 2 C 3.
Total work 12.
Total efficiency 6.
Finished together 12 Ã· 6 = 2day satisfied
**B alone do in 12 Ã· 2 = 6 days.

Manohar said:   5 years ago
Simply:

6:3:1 = 9
9*2 = 18.

18/3 = 6.
(1)

Rajshekar said:   5 years ago
A x.
B 2x.
C 3x.

A+B+B = 1/2,
X+2x+3x = 1/2.
6x=1/2.
X=1/12.

So, be alone =2x = 2 * 1/12 = 1/6 = 6days.
(3)

Rexi said:   5 years ago
Simply, it is solved by;

A=2B ; A=3C.
A/2=B ; A/3=C ---> time,
2/A=B; 3/A=C ---> efficiency,
1/A+2/A+3/A = 1/2 ---> A+B+C=1/2.
A = 12,
B = 6,
C = 4.
(3)