**QUESTION: **The ratio of the ages of Kemah compared to Bob and Deborah is 1∶2∶4. Deborah is 21 years older than Kemah. Work out the ages of Kemah, Bob, and Deborah.

**ANSWER:** We know that difference between Deborah’s and Kemah’s ages is 21. Looking at the ratio, Kemah has 1 part and Deborah has 4, meaning that the difference between them (21 years) constitutes 3 parts in the ratio. Therefore, we get that

\text{1 part }=21\div 3=7

Kemah, Bob, and Deborah have 1, 2, and 4 parts in the ratio respectively. So, we get that

\text{Kemah’s age }=1\times 7=7

\text{Bob’s age }=2\times 7=14

\text{Deborah’s age }=4\times 7=28