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 1 of 3.
Atul1487 said:
1 decade ago
Simple method without any rubbish ratio.
Suppose B completes 1 work in x days.
So B completed work in 1 day = 1/x.............1.
Now A completes 1 work = x/2 (Cz A is twice faster than B).
So A completed work in 1 day = 2/x.............2.
Together their Work = 1/x + 2 /x.
Given x = 12.
So,
Together their Work = 1/12 + 2 /12.
== 1/12 + 1/6.
==1/4 or 4 days.
No ratio - nothing complicated.
Suppose B completes 1 work in x days.
So B completed work in 1 day = 1/x.............1.
Now A completes 1 work = x/2 (Cz A is twice faster than B).
So A completed work in 1 day = 2/x.............2.
Together their Work = 1/x + 2 /x.
Given x = 12.
So,
Together their Work = 1/12 + 2 /12.
== 1/12 + 1/6.
==1/4 or 4 days.
No ratio - nothing complicated.
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.)
Aditya said:
3 years ago
A finished work in 6 days.
B finishes work in 12 days.
Calculating LCM we get 12 which is total work.
Now, work efficiency of A = 12/6 = 2 unit/day,
work efficiency of B = 12/12 = 1 unit/day,
working together A+B = 2+1 = 3unit/day,
Therefore for finishing 12 unit work together they need 12/3 = 4 days.
B finishes work in 12 days.
Calculating LCM we get 12 which is total work.
Now, work efficiency of A = 12/6 = 2 unit/day,
work efficiency of B = 12/12 = 1 unit/day,
working together A+B = 2+1 = 3unit/day,
Therefore for finishing 12 unit work together they need 12/3 = 4 days.
(5)
Manzoor said:
5 years ago
No @Veer
According to me, the solution is;
2A=B in time.
There, the efficiency is inversely proportional to time.
Efficiency of A:B = 1:2
Total work is done by B = No of day's * efficiency
= 12*2 = 24.
If together done the same work= 24÷3.
= 8 days.
Please correct me, If I am wrong.
According to me, the solution is;
2A=B in time.
There, the efficiency is inversely proportional to time.
Efficiency of A:B = 1:2
Total work is done by B = No of day's * efficiency
= 12*2 = 24.
If together done the same work= 24÷3.
= 8 days.
Please correct me, If I am wrong.
Umeshprasad said:
1 decade ago
Let A's 1 day work is x
B's 1 day work is 1/12
from question a is twice as fast as B
so A=2B------------(1)
x=2*1/12=>1/6
which is one day work of A
combine one day work of A and B is (1/6)+(1/12)
which will give u 1/4
so the entire work they will finish in 4 day.
B's 1 day work is 1/12
from question a is twice as fast as B
so A=2B------------(1)
x=2*1/12=>1/6
which is one day work of A
combine one day work of A and B is (1/6)+(1/12)
which will give u 1/4
so the entire work they will finish in 4 day.
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.
Ghousia said:
1 decade ago
simplest method:
A is twice of B then B=2A
B completes work in=12
then 2A=12=>A=6
A's 1 day work=1/6, B's 1 day work=1/12
(A+B)'s 1 day work=(1/6+1/12)=3/12=1/4
now (A+B) together finish work in 4days
A is twice of B then B=2A
B completes work in=12
then 2A=12=>A=6
A's 1 day work=1/6, B's 1 day work=1/12
(A+B)'s 1 day work=(1/6+1/12)=3/12=1/4
now (A+B) together finish work in 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.
Karthick M said:
3 years ago
Easiest method to solve this type of problem..
Given. A=2B.
(A+B)'s 1day work = 1/12=(2B+B)'s 1day work
3B's 1day work =1/12.
B's 1-day work =1/4.
So, B's whole work done is 4 days.
Given. A=2B.
(A+B)'s 1day work = 1/12=(2B+B)'s 1day work
3B's 1day work =1/12.
B's 1-day work =1/4.
So, B's whole work done is 4 days.
(1)
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.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers