Question

A mother who is 40 years old has a daughter and a son. The son is twice as old as the daughter. In 15 years the sum of all their ages will be 100 years. How old are the siblings now?

Answer 1

15 and 5

Explanation:

Mother's current age: 40

daughter's age: d

son's age: s

son is 2x as old as daughter: s = 2d

Then, 15 years from now, the sum of their ages will be:

(40 + 15) + (2d + 15) + (d + 15) = 100

or

55 + 15 + 15 + 3d = 100

85 + 3d = 100, or 3d = 15, or d = 5.

Then the son's age is 3(5) = 15 and the daughter's is 5.

Answer 2

the son is 30 and the daughter is 15

Explanation:

the mom is 55 in 15 years

100-55=45

45-30=15

15x2=30