Let the present age of father and son be x and y years respectively.

From 1st condition,
(x - 4) = 5(y- 4)
⇒ x - 4 = 5y - 20
⇒ x - 5y = -16 .....(i)

From 2nd condition,
⇒ x + y = 44 ...(ii)

Correct Option: B

Let the present age of father and son be x and y years respectively.

From 1st condition,
(x - 4) = 5(y- 4)
⇒ x - 4 = 5y - 20
⇒ x - 5y = -16 .....(i)

From 2nd condition,
⇒ x + y = 44 ...(ii)

From equation (i) and (ii)
-6y = -60
⇒ y = 10

∴ Present age of son = 10 years

Let B's present age be x years then A's present age be (x + 9) years
As per the given condition
(x + 9 + 10) = 2(x - 10)

Correct Option: A

Let B's present age be x years then A's present age be (x + 9) years
As per the given condition
(x + 9 + 10) = 2(x - 10)
⇒ x = 39

∴ The present age of B = 39 years

Let the respective ages of A, B and C, ten years ago be x, 2x and 3x years.
∵ (x + 10) + (2x + 10) + ( 3x + 10) = 90

Correct Option: A

Let the respective ages of A, B and C, ten years ago be x, 2x and 3x years.
∵ (x + 10) + (2x + 10) + ( 3x + 10) = 90
⇒ 6x = 60
⇒ x = 10
∴ B's present age = 2x + 10 = 30 years

Let father's age be x years and the sum of ages of children be y years.
∵ x = 4 y ....(i)
Also (x + 6) = 2(y + 6 + 6 + 6) ....(ii) [6 is added thrice for three children ]

Correct Option: C

Let father's age be x years and the sum of ages of children be y years.
∵ x = 4 y ....(i)
Also (x + 6) = 2(y + 6 + 6 + 6) ....(ii) [6 is added thrice for three children ]

Solving (i) and (ii)
x = 60 years, and y = 15 years.

According to the formula.
Required time = (x + y)/(u - v)
Here , x = 50 m , y = 65 m , u = 18 m/s and v = 17 m/s

Correct Option: D

According to the formula.
Required time = (x + y)/(u - v)
Here , x = 50 m , y = 65 m , u = 18 m/s and v = 17 m/s
∴ Required time = (50 + 65)/(18 - 17) = 115/ 1 = 115 s