Let Tarun and Varun's ages are 3k yr and 7k yr, respectively.
∴ 7k + 4 = 39

Correct Option: D

Let Tarun and Varun's ages are 3k yr and 7k yr, respectively.
∴ 7k + 4 = 39
⇒ k = 5

Hence, Tarun's age 4 yr ago = 3 x 5 - 4 = 11 yr

Let 10 yr ago, ages of Ram and Rahim were k yr and 3k yr, respectively.
Then, present age of Ram = (k + 10)
and present age of Rahim = (3k + 10)
According to the question, (k + 10 + 5) / (3k + 10 + 5) = 2/3

Correct Option: B

Let 10 yr ago, ages of Ram and Rahim were k yr and 3k yr, respectively.
Then, present age of Ram = (k + 10)
and present age of Rahim = (3k + 10)
According to the question, (k + 10 + 5) / (3k + 10 + 5) = 2/3
⇒ 3k + 45 = 6k + 30
⇒ 3k = 15
∴ k = 5
Hence, required ratio = (5 + 10) / (3 x 5 + 10)
= 15/25
= 3 : 5

Let k yr before, the ratio of their ages was 3 : 5.
According to the question
(40 - k)/(60 - k) = 3/5

Correct Option: D

Let k yr before, the ratio of their ages was 3 : 5.
According to the question
(40 - k)/(60 - k) = 3/5
⇒ 200 - 5k = 180 - 3k
⇒ 2k = 20
∴ k = 10

Let present age of Ravi be k.
Then, Present age of Ravi's father = 4k.
Now, 5 yr ago,
Ravi's father's age = 7 x Ravi's age
⇒ 4k - 5 = 7(k - 5)

Correct Option: C

Let present age of Ravi be k.
Then, Present age of Ravi's father = 4k.
Now, 5 yr ago,
Ravi's father's age = 7 x Ravi's age
⇒ 4k - 5 = 7(k - 5)
⇒ 4k - 5 = 7k - 35
⇒ 3k = 30
∴ k = 10
∴ Ravi's present age = k = 10 yr
∴ Ravi's father's present age = 4k
= 4 x 10 = 40 yr

3 yr before, total age of 5 members = 17 x 5 = 85 yr
∴ The present age of all members of family = 85 + 3 x 5 = 100 yr

Let the age of child be N yr.
∴ Present average age of family including the child
= (100 + N)/6

Correct Option: D

3 yr before, total age of 5 members = 17 x 5 = 85 yr
∴ The present age of all members of family = 85 + 3 x 5 = 100 yr

Let the age of child be N yr.
∴ Present average age of family including the child
= (100 + N)/6
⇒ 17 = (100 + N)/6
∴ N = 102 - 100 = 2 yr