Question

The strength of a cable is proportional to the square of its diameter. If a 2-cm cable will support 800kg, how much will a 3-cm cable support?

Answer 1

strength [is proportional to] d^2
strength1/(d1)^2 = strength2/(d2)^2
800kg/(2cm)^2 = strength2/(3cm)^2
strength2 = 800 kg * (3 cm)^2/(2 cm)^2
strength2 = 800 kg * 3^2/2^2
strength2 = 800 kg * 9/4
strength2 = 1800 kg