How far from her toes is her centre of gravity?

Question

This athlete found that 0.72 of her weight was supported by her forearms and 0.28 by her toes, i.e. the total normal forces on her forearms and toes respectively are 0.720w and 0.280w, where w is her weight. The athlete is 1.65m tall (Distance A) and in plank position Distance B, which measures from her toes to middle of her forearms, is 1.38m. 

A : 0.994m from her toes is her centre of gravity. 

B : 0.994m from her head is her centre of gravity.

C : 1.19m from her toes is her centre of gravity.

D : 0.387m from her toes is her centre of gravity.

Answer 1

Answer is A

Draw a diagram

Sum Torque at Toes = 0

0.720W * 1.38 - W * X = 0

Solve for X, X = 0.994m from the toes.

Let me know if you need me to post the diagram showing how the sum of torque equation plays out.