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.
Amrit said:
7 years ago
suppose B =x;
and A works twice =2x,
then the total amount of work is;
2x+x=12;
3x=12,
x = 4.
and A works twice =2x,
then the total amount of work is;
2x+x=12;
3x=12,
x = 4.
Arnab said:
8 years ago
A works twice as fast as B means,
The efficiency of A : B = 2:1 (efficiency means per day work),
A does in 1 day 2 units work.
B does in 1 day 1 unit work.
(A+B) together do in 1 day = 3 units work.
Total work = 1* 12 = 12 units (as per question B can complete a work in 12 days).
(A+B) can do together = 12/ 3 days = 4 days. (Ans.)
The efficiency of A : B = 2:1 (efficiency means per day work),
A does in 1 day 2 units work.
B does in 1 day 1 unit work.
(A+B) together do in 1 day = 3 units work.
Total work = 1* 12 = 12 units (as per question B can complete a work in 12 days).
(A+B) can do together = 12/ 3 days = 4 days. (Ans.)
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.
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.
Kashish said:
9 years ago
More easy solution Guys.
Let assume that B take X time, so A will take 2X.
So now there 1 Days work will 1/x + 2/x = 3/x.
Now from question, they work for 12 days,
3/x = 12.
x = 3/12.
x = 4 ->Answer.
Let assume that B take X time, so A will take 2X.
So now there 1 Days work will 1/x + 2/x = 3/x.
Now from question, they work for 12 days,
3/x = 12.
x = 3/12.
x = 4 ->Answer.
Inna Reddy Chilakala said:
10 years ago
A : B = 2 : 1 (work).
B = 12.
A can finish work 1 --- 12.
2 ---- 6.
A+B = 12*6/12+6 = 4.
B = 12.
A can finish work 1 --- 12.
2 ---- 6.
A+B = 12*6/12+6 = 4.
Deepa said:
1 decade ago
A:B = 1:2.
B can complete a work in 12 days.
Let A can complete in X days.
X:12 = 1:2.
X = 1*12/2.
X = 6 i.e, A = 6.
(A+B) 1 day work = 1/6+1/12 = 1/4.
So, A and B finish work in 4 days.
B can complete a work in 12 days.
Let A can complete in X days.
X:12 = 1:2.
X = 1*12/2.
X = 6 i.e, A = 6.
(A+B) 1 day work = 1/6+1/12 = 1/4.
So, A and B finish work in 4 days.
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.
Swati said:
1 decade ago
SHORTCUT:
A is twice efficient as B that means If B takes 12 days then A will take 6 days.
Now both are working together. So definitely together they'll take less than 6 days. ONLY option less than 6 days is Option A i.e. 4 days.
A is twice efficient as B that means If B takes 12 days then A will take 6 days.
Now both are working together. So definitely together they'll take less than 6 days. ONLY option less than 6 days is Option A i.e. 4 days.
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