Question

Five years ago, A's age was four times the age of B. Five years hence, A's age will be twice the age of B. Find their present ages.​

Answer 1

Let us consider B’s age = X

Then A’s age = 4X

Five years ago

⇒ A’s age = 4X + 5

⇒ B’s age = X + 5

Five years hence

⇒ A’s age = 4X + 5 + 5

⇒ A’s age = 4X + 10

⇒ B’s age = X + 5 + 5

⇒ B’s age = X + 10

From the given question

4X + 10 = 2(X + 10)

4X + 10 = 2X + 20

4X – 2X = 10

2X = 10

X = 5

A’s age = 4X + 5

A’s age = 25 years

B’s age = X + 5

B’s age = 10 years.

Answer 2

Let us consider B’s age = X

Then A’s age = 4X

Five years ago

⇒ A’s age = 4X + 5

⇒ B’s age = X + 5

Five years hence

⇒ A’s age = 4X + 5 + 5

⇒ A’s age = 4X + 10

⇒ B’s age = X + 5 + 5

⇒ B’s age = X + 10

From the given question

4X + 10 = 2(X + 10)

4X + 10 = 2X + 20

4X – 2X = 10

2X = 10

X = 5

A’s age = 4X + 5

A’s age = 25 years

B’s age = X + 5

B’s age = 10 years.