The ratio of Tenzin's age to his father's age is $2 : 7$. His father is 35 years old. How old is Tenzin?

Explanation

1. 01

   The father's 7 parts are 35 years, so one part is $35 \div 7 = 5$ years.

2. 02

   Tenzin has 2 parts: $2 \times 5 = 10$ years.