Practice!

Sample Problem

The average height of Sally, Jackson, Tina and David is 150 cm per person. The average height of Sally, Jackson and Tina is 145 cm per person. Tina is 5 cm taller than David. Jackson is 4/5 as tall as David. How tall is Sally?

  cm

Solution

The total height of all the people: 150 × 4 = 600 cm

The total height of Sally, Jackson and Tina: 145 × 3 = 435 cm

Therefore, David’s height: 600 – 435 = 165 cm

Tina’s height: 165 + 5 = 170 cm

Jackson’s height: 170 × 4/5 = 136 cm

Therefore, Sally’s height: 600 – 165 – 170 – 136 = 129 cm