Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 24)
24.
A works twice as fast as B. If B can complete a work in 12 days independently, the number of days in which A and B can together finish the work in :
Answer: Option
Explanation:
Ratio of rates of working of A and B = 2 : 1.
So, ratio of times taken = 1 : 2.
| B's 1 day's work = | 1 | . |
| 12 |
 A's 1 day's work = |
1 | ; (2 times of B's work) |
| 6 |
| (A + B)'s 1 day's work = |  |
1 | + | 1 |  |
= | 3 | = | 1 | . |
| 6 | 12 | 12 | 4 |
So, A and B together can finish the work in 4 days.
Discussion:
28 comments Page 2 of 3.
Arun Pandian said:
1 decade ago
SHORT CUT METHOD:
let x=2(bcz A is twice as fast as B)
n=12(bcz B completes the work in 12 days)
use the formula:A&B together do the work in p days as follows
p=n/x+1
=12/3
=4days
let x=2(bcz A is twice as fast as B)
n=12(bcz B completes the work in 12 days)
use the formula:A&B together do the work in p days as follows
p=n/x+1
=12/3
=4days
Aravind_appu said:
1 decade ago
A = 2b------(1).
B = 1/12------(2).
1 sub in 2.
A = 2(1/12).
A = 1/6.
Total work is done TH = A+B.
TH = (1/6+1/12).
= (12+6)/(6*12).
= (18/72).
= 1/4.
= 4 day exactly.
B = 1/12------(2).
1 sub in 2.
A = 2(1/12).
A = 1/6.
Total work is done TH = A+B.
TH = (1/6+1/12).
= (12+6)/(6*12).
= (18/72).
= 1/4.
= 4 day exactly.
Vaishnavi Kokate said:
9 years ago
Let,
A = 20
B = 10 because A works twice as fast as B.
Total work, B = 10 * 12=120 because B completes his work in 12 days.
so A + B/total work.
120/30 = 4 days.
A = 20
B = 10 because A works twice as fast as B.
Total work, B = 10 * 12=120 because B completes his work in 12 days.
so A + B/total work.
120/30 = 4 days.
Omkar said:
1 decade ago
A = 2B.
Hence,
A+B = 2B + B
i.e. as good as three Bs working together.
B completes in 12 Days,
3B will take 1/3rd of the time i.e. 12/3 = 4.
Hence,
A+B = 2B + B
i.e. as good as three Bs working together.
B completes in 12 Days,
3B will take 1/3rd of the time i.e. 12/3 = 4.
Deepa said:
1 decade ago
B'S one day work=1/12
A'S one day work=2(1/12)=1/6
(A+B) one day work=(1/12)+(1/6)=1/4
hence A and B together complete the work in 4 days
A'S one day work=2(1/12)=1/6
(A+B) one day work=(1/12)+(1/6)=1/4
hence A and B together complete the work in 4 days
Sudhanshu said:
9 years ago
T --------- W
B --------- 1 1/12
A ---------1 1/6
If A+B work
W --------- T( days)
1/4 --------- 1/1/4.
It comes 4days.
B --------- 1 1/12
A ---------1 1/6
If A+B work
W --------- T( days)
1/4 --------- 1/1/4.
It comes 4days.
Sudhanshu said:
9 years ago
T --------- W
B --------- 1 1/12
A ---------1 1/6
If A+B work
W --------- T( days)
1/4 --------- 1/1/4.
It comes 4days.
B --------- 1 1/12
A ---------1 1/6
If A+B work
W --------- T( days)
1/4 --------- 1/1/4.
It comes 4days.
Roy said:
4 years ago
@All.
Given A=2B.
B's 1 day work = 1/12,
So A's 1 day work=2*1/12=1/6.
(a+b)1 day = 1/6 + 1/12 = 1/4,
Hence 4 days.
Given A=2B.
B's 1 day work = 1/12,
So A's 1 day work=2*1/12=1/6.
(a+b)1 day = 1/6 + 1/12 = 1/4,
Hence 4 days.
(3)
Pedada PavanGovind said:
2 years ago
A:B is 24:12 = 1:2 =>3 total efficiency.
Given B complete in 12 days.
Then together work in 12/3 = 4 days.
Given B complete in 12 days.
Then together work in 12/3 = 4 days.
(4)
Veer said:
5 years ago
The easiest way:
A : B = 2 : 1 (work).
B = 12.
A can finish work 1 --- 12.
2 ---- 6.
A+B = 12*6/12+6 = 4.
A : B = 2 : 1 (work).
B = 12.
A can finish work 1 --- 12.
2 ---- 6.
A+B = 12*6/12+6 = 4.
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