Efficiency of A = 12.5%
Efficiency of B = 6.25%
Efficiency of C = 1.25%

Efficiency of (A+ B + C) = (12.5 +6.25 + 1.25) = 20%

Correct Option: A

Efficiency of A = 12.5%
Efficiency of B = 6.25%
Efficiency of C = 1.25%

Efficiency of (A+ B + C) = (12.5 +6.25 + 1.25) = 20%
Required no of days = 100/20 = 5 days

12 men can complete 1/3 of the work in 3 days and the remaining 2/3 of the work in 6 days.
1 man can complete 2/3 of the work in (12 x 6) = 72 days

Correct Option: D

12 men can complete 1/3 of the work in 3 days and the remaining 2/3 of the work in 6 days.
1 man can complete 2/3 of the work in (12 x 6) = 72 days
∴ (12 - 2 + 6) = 16 men can complete 2/3 of thye work in 72/16 = 4¹/₂ days

(A + B + C)' S 1 day's work = (1/24) + (1/6) + (1/12) = 7/24

Correct Option: A

(A + B + C)' S 1 day's work = (1/24) + (1/6) + (1/12) = 7/24
∴ (A + B + C) can do the entire work in = 24/7
= 3³/₇ days

A's 10 day's work = 10 x (1/25) = 2/5
Remaining work = 1 - 2/5 = 3/5
Work was done by (A + B) in 1 day = (1/25 + 1/20) = 9/100
∴ 3/5 work was done by (A + B) in (100/9 x 3/5) = 20/3 days

Correct Option: D

A's 10 day's work = 10 x (1/25) = 2/5
Remaining work = 1 - 2/5 = 3/5
Work was done by (A + B) in 1 day = (1/25 + 1/20) = 9/100
∴ 3/5 work was done by (A + B) in (100/9 x 3/5) = 20/3 days

Hence, the work lasted for (10 + 6²/₃) = 16²/₃ days.

A's 10 day's work = (10 x 1/80) = 1/8
Remaining work = (1 - 1/8) = 7/8
∵ 7/8 work is done by B in 42 days
⇒ Whole work will be done by B in (42 x 8/7) = i .e., 48 days.

Correct Option: C

A's 10 day's work = (10 x 1/80) = 1/8
Remaining work = (1 - 1/8) = 7/8
∵ 7/8 work is done by B in 42 days
⇒ Whole work will be done by B in (42 x 8/7) = i .e., 48 days.
∴ (A + B)'s day's work = (1/80 + 1/48) = 8/240 = 1/30
Hence, A and B together can finish it in 30 days.