Question

A is four times as old as B. Ten ) years as B. Ten years ago. A was Yo times as old as B. Find their present ages.
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Answer 1

Let B be x years old.

.

Now:

B = x

A = 4x

.

Ten years ago,:

B = x - 10

A = 4x - 10

.

Ten years ago, A was 10 times as old as B:

4x - 10 = 10 (x - 10)

.

Solve x:

4x - 10 = 10 (x - 10)

4x - 10 = 10x - 100

10x - 4x = 100 - 10

6x = 90

x = 15

.

Find their present age:

B = x = 15

A = 4x = 4(15) = 60

.

Answer: B is 15 years old.

Answer 2

Let present age of B be X year's.

Present age of A = 4 × Present age of B = 4X year's.

Before 10 year's age of A = Present age of A - 10 = ( 4X - 10) year's.

Before 10 year's age of B = Present age of B - 10 = ( X - 10 ) year's .

According to question,

Before 10 year's age of A = 10 ( Before 10 year's age of B ).

4X - 10 = 10 ( X - 10)

4X - 10 = 10X - 100

10X - 4X = -10 + 100

6X = 90

X = 90/6

X = 15 year's.

Present age of B = X = 15 year's.