Aptitude - Time and Work - Discussion

Discussion Forum : Time and Work - General Questions (Q.No. 9)
9.
A does 80% of a work in 20 days. He then calls in B and they together finish the remaining work in 3 days. How long B alone would take to do the whole work?
23 days
37 days
371/2
40 days
Answer: Option
Explanation:

Whole work is done by A in ( 20 x 5 ) = 25 days.
4

Now, ( 1 - 4 ) i.e., 1 work is done by A and B in 3 days.
5 5

Whole work will be done by A and B in (3 x 5) = 15 days.

A's 1 day's work = 1 , (A + B)'s 1 day's work = 1 .
25 15

Therefore B's 1 day's work = ( 1 - 1 ) = 4 = 2 .
15 25 150 75

So, B alone would do the work in 75 = 37 1 days.
2 2

Discussion:
164 comments Page 1 of 17.

Abhijeet said:   3 years ago
A can do 80% of work in 20 Days.

So, 20 days = 80%,
1 day = ?
= 4%,

A and B worked for 3 days so 4% A can do in 1 day and in 3 days it is 3*4=12%.
A and B together worked and completed the remaining 20% of the work in 3 days which A work is 12%.

So, A+B =20%,
12% +B =20,
B = 8%,
B worked 8% in 3 days,
3 days = 8%,
1 day = ?
=2.66%.

The whole work is 100% in itself,
B 100/2.66 ==37.5 or 37 1/2.
(143)

Karan said:   2 years ago
A = 80% in 20 days.
80% = 80/100 = 4/5.
A = 4% Daily work.

80-100 = 20% of work remaining.
20% of work done by A+B in 3 days.

A = 4% Daily work in 3 days.
A = 4×3=12%.
20 - 12 = 8%.
B = 8%.
B = 8/100%×3 = 37.5 = 37 1/2.
(95)

Keerthan G said:   2 years ago
A= 80% in 20 days.
100% in 25 days.

A + B = 20% in 3 days.
100% in 15 days.

LCM OF 15 and 25 is 75.

Efficiency of A is 75/25 = 3.
Efficiency of A+B is 75/15 = 5.

A+B = efficiency of A+B is 5 so that,

A+B = 5,
3+B = 5,
B = 2.

THEN 75 IS TOTAL WORKS.

So, 75/2 = 37.5.
(77)

Keerthu said:   11 months ago
A in 80% work done 20 days.
A in 100% work done 100*20/80= 25 days.

A+B in 20% work done 3 days.
A+B in 100% work done 100*3/20= 15 days.
A = 25 days.
A+B = 15 days.

LCM OF 75.
1 DAY OF WORK 75/25 = 3
1 DAY A+B WORK 75/15 = 5.
A + B = 5
3 + B = 5
B = 2
B total working days =>75/2 = 37.5 days.
(50)

Aliya said:   9 months ago
A's work rate = 80% in 20.days =80%/20=4
Remaining work of A and B = 100%-80%= 20% in 3 days = 20%/3.
B can do work = 20/3 - 4 = 20-12/3 = 8/3%.
B 100% work = 100/8/3 = 37.5 days.
(32)

Suhas Sawant said:   3 years ago
In the case of A,

80 %. = 20 days
So
100% = ?

Cross multiplication
= 100 *20 /80
= 25 days.

So, A has the power to do daily;
100/25 = 4 % of the work.

As given
80 % of the work is done by A,
for the Remaining 20% of work, he calls B to finish work in 3 days.

In 3 Days, 'A' worked by using his power of 4% and did 4* 3 = 12

The remaining 20 -13 = 8 % will be completed by 'B' in 3 days
B' will work,
8 %. = 3 Day
100% =. ?

Crossing
= 100* 3/8
= 75/2,
= 37.5
And the answer is 37 and a half means i.e. 37 1/2.
(30)

Krishnaveni said:   2 years ago
80%--->20days.
20%--->'x' days.
x = [20 * 20%]/80%.
x = 5 days.
1/5 + 1/y = 1/3.
1/y = 2/15.
20%--->15/2 days.
100%--->'z' days.
z = [(15/2) * 100%]/20%.
z = 75/2 days.
(30)

VATHSA said:   3 years ago
80% in 20days.

100% in ? ==>25 days.
A's work per day = 1/25,
A completes 80% of work = remaining 20% of work = 20/100 of 1 = 1/5.

Together they complete in 3 days.
(1/25 + 1/B) *3= 1/5
SOLVE:
1/B = 2/75 = B's work per day.
For B to complete = 75/2 = Answer.
(23)

Keshav T said:   3 years ago
A = 20/(80/100)=20/(4/5)
A = 20*5/4.
A = 25 days i.e 1/25 days.
1-(4/5 )work is done = 1/5.
A+B = 1/15.
1/15 - 1/25 = 2/75.
75/2 i e 37(1/2) days.
(21)

Deepa said:   3 years ago
A:
80% in 20 days then
100% in x days
Cross multiply them you will get 25days

A+B:

20% in 3 days then
100% in y days
Cross multiply them you will get y=15.
Now: A's one day work is 1/25.
& A+B's one-day work is 1/15.

A+B one day work minus A one day work =1/15 - 1/25 = 75/2.
(16)


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