Question

a heater uses3 units of electricity in 40 minutes . how many units does it usein 2 hours

Answer 1

In 2 hours it uses 9 units of electricity

Answer 2

2 hours = 120 mins
Electricity used by a heater in 40 mins = 3
Electricity used by a heater in 1 min = 3/40
Electricity used by a heater in 120 mins = 3/40×120 = 9 units

Hope it helps you!