The average of three numbers is 70. The first is twice the second and the second is twice the third. What is the smallest of the three numbers?

Explanation

1. 01

   Let the third number be x; then the second is 2x and the first is 4x.

2. 02

   Total = $x + 2x + 4x = 7x = 3 \times 70 = 210$.

3. 03

   $x = 30$, so the numbers are 120, 60 and 30.