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

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