25 men and 15 women can complete, a piece of work in 12 days.
∴ Work done by them in 8 days = 8/12 = 2/3
Remaining work is completed by 25 men in 6 days
∴ Time taken by 25 men to complete the whole work = 3 x 6 = 18 days

Correct Option: D

25 men and 15 women can complete, a piece of work in 12 days.
∴ Work done by them in 8 days = 8/12 = 2/3
Remaining work is completed by 25 men in 6 days
∴ Time taken by 25 men to complete the whole work = 3 x 6 = 18 days

From the question
Time taken by 15 women to complete the whole work = 1 / (1/12 - 1/18)
= 1 / {(3 - 2) / 36} = 36/(3 - 2) = 36 days

Efficiency ( per minute) of Modi = 4 copies/min
Efficiency of Modi and Xerox together = 10 pages/min
∴ Efficiency of Xerox alone = 10 - 4 = 6 pages/min

Correct Option: B

Efficiency ( per minute) of Modi = 4 copies/min
Efficiency of Modi and Xerox together = 10 pages/min
∴ Efficiency of Xerox alone = 10 - 4 = 6 pages/min
∴ Mr. Xerox needs 6 min to copy 36 pages.

Since, 50 men can do a job in 50 days.
So, work done by 1 man in a day = 1/(50 x 50)

Also, 80 women can do the job in 50 days.
So, work done by 1 women in 1 day = 1/(50 x 80)

Now, work done by 40 men and 48 women in first 10 days
= (40 x 10)/(50 x 50) + (48 x 10)/(50 x 80)
= 4/25 + 3/25 = 7/25

Now, 5 men and 8 women are removed after 10 days,
So work done by 35 men and 40 women in 10 days = (35 x 10)/(50 x 50) + (40 x 10)/(50 x 80)
= 7/50 + 1/10 = (7 + 5)/50
= 6/25

Again, 5 men and 8 women are removed after 10 days,
So work done by 30 men and 32 women in 10 days = (30 x 10)/(50 x 50) + (32 x 10)/(50 x 80) = 5/25

Now, after every 10 days as the number of men and
women decrease, work done also decreased by 1/25th past.
So, work done after every 10 days upto 50 days = 7/25 + 6/25 + 5/25 + 4/25 + 3/25
= 25/25 = 1

Correct Option: B

Since, 50 men can do a job in 50 days.
So, work done by 1 man in a day = 1/(50 x 50)

Also, 80 women can do the job in 50 days.
So, work done by 1 women in 1 day = 1/(50 x 80)

Now, work done by 40 men and 48 women in first 10 days
= (40 x 10)/(50 x 50) + (48 x 10)/(50 x 80)
= 4/25 + 3/25 = 7/25

Now, 5 men and 8 women are removed after 10 days,
So work done by 35 men and 40 women in 10 days = (35 x 10)/(50 x 50) + (40 x 10)/(50 x 80)
= 7/50 + 1/10 = (7 + 5)/50
= 6/25

Again, 5 men and 8 women are removed after 10 days,
So work done by 30 men and 32 women in 10 days = (30 x 10)/(50 x 50) + (32 x 10)/(50 x 80) = 5/25

Now, after every 10 days as the number of men and
women decrease, work done also decreased by 1/25th past.
So, work done after every 10 days upto 50 days = 7/25 + 6/25 + 5/25 + 4/25 + 3/25
= 25/25 = 1

So, it will take 50 days for them to complete the work.

A's 1 days 's work = 1/8
B ' s 1 days ' s = 1/10
C ' s day 's work = 1/20
(A + B + C)'s 1 days 's work = 1/8 + 1/10 + 1/20 = (5 + 4 + 2)/40 = 11/40

Correct Option: A

A's 1 days 's work = 1/8
B ' s 1 days ' s = 1/10
C ' s day 's work = 1/20
(A + B + C)'s 1 days 's work = 1/8 + 1/10 + 1/20 = (5 + 4 + 2)/40 = 11/40
∴ (A + B + C ) can finish the work in 40/11 days or 3 ⁷/₁₁ days.

Let the original number of men = N
Time taken by N = 80 days
Now, (N - 10) men can finish the work in the (80 + 20) = 100 days
Here, M₁ = N, M₂ = (N - 10), D₁ = 80 and D₂ = 100
According to the formula.
M₁D₁ = M₂D₂

Correct Option: B

Let the original number of men = N
Time taken by N = 80 days
Now, (N - 10) men can finish the work in the (80 + 20) = 100 days
Here, M₁ = N, M₂ = (N - 10), D₁ = 80 and D₂ = 100
According to the formula.
M₁D₁ = M₂D₂
⇒ N x 80 = 100 x (N - 10)
⇒ 8N = 10N - 100
⇒ 10N - 8N = 100
⇒ N = 50