Question

a boy is y years old . his sister is thrice as old as he is the sum of their ages Is 24 how old is the body?​

Answer 1

Question :-

• A boy is y years old. His sister is thrice as old as her. The sum of their ages is 24. How old is the boy?

Answer :-

• The age of the boy is 6 years.

To find :-

• The age of the boy.

Solution :-

• It is given that the age of the boy is "y" years and his sister is thrice as old as him.

Hence :-

• The age of his sister will be "3y" years.

It is also given that :-

• The sum of their ages is 24 years.

Therefore,

$: \longmapsto\tt y + 3y = 24$

$: \longmapsto \tt4y = 24$

Transposing 4 from LHS to RHS, changing it's sign,

$: \longmapsto \tt y = \dfrac{24}{4}$

$: \longmapsto\underline{ \boxed{ \tt y = 6}}$

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Hence :-

$\sf The \: boy's \: age = y = 6 \: years.$

$\sf His \: sister's \: age = 3y = 3 \times 6 = 18 \: years.$