Question

A toaster uses 1400 watts and takes 2.30 minutes to cook a piece of bread. If electricity costs
$0.16 / (kW•hr), then how many pieces of bread can be cooked for $0.05.

Answer 1

Total energy used = $1.4\times\frac{2.3}{60}=0.0536\ kW\ h$

No. Of pieces of bread in 1 kW h= $\frac{1}{0.0536}=18.63\ pieces$

So, 0.16\$\ produces 18.63 pieces of bread

Then, $0.05\$$ will produce $\frac{18.63\times0.05}{0.16}=5.82\ pieces$