let the work done be 1 work.
Here M1=15, D1=16 W1=W2 =1
M2 =24 D2= ?
∴ According to the formula
M1 D1 W2 = M2 D2 W1

Correct Option: C

let the work done be 1 work.
Here M1=15, D1=16 W1=W2 =1
M2 =24 D2= ?
∴ According to the formula
M1 D1 W2 = M2 D2 W1
⇒ 15 x 16 x 1 = 24 x D2 X 1
∴ D1 = 15 X 16/24 = 10
Therefore 10 days are required to complete the work

Work done by (A + B) in 1 day = 1/24
Work done by B alone in 1 day = 1/(3 x 12) = 1/36
∴ Work of A for 1 day = 1/24 - 1/36 = 1/72
After 12 days the remaining work = 1 - 1/3 = 2/3

Correct Option: A

Work done by (A + B) in 1 day = 1/24
Work done by B alone in 1 day = 1/(3 x 12) = 1/36
∴ Work of A for 1 day = 1/24 - 1/36 = 1/72
After 12 days the remaining work = 1 - 1/3 = 2/3
∵ 1/72 work is done by A in 1 day
∴ 2/3 work is done by A in (1 x 72)/(1 x 2/3) = 48 days

Let B takes x days to do the work
∴ A takes (2 x 3 / 4 x) = 3 x / 2 days to do it
∵ (A + B)'s 1 day's work = 1 / 18

Correct Option: C

Let B takes N days to do the work
∴ A takes 2 x (3/4) x N = 3N/2 days to do it
∵ (A + B)'s 1 day's work = 1/18
⇒ 1/N + 2/3N = 1/18
∴ N = 30

Radio of times taken = (1/3) : (1/4)

Correct Option: C

Radio of times taken = (1/3) : (1/4) = 4 : 3

∵ Mohan moves the whole lawn in x hours.
⇒ mohan moves in 2 hours = 2/x part of the lawn.

Correct Option: D

∵ Mohan moves the whole lawn in x hours.
⇒ mohan moves in 2 hours = 2/x part of the lawn.
∴ Unmoved part = 1 - 2/x = (x - 2)/ x part