Two people is 1/2 as many as 4 people: 2 ÷ 4 = \(\frac{\mathrm{1} }{\mathrm{2}}\) .
Multiply the number of machines 4 people can run by \(\frac{\mathrm{1} }{\mathrm{2}}\) to determine how many machines 2 people can run: 8 × \(\frac{\mathrm{1} }{\mathrm{2}}\) = 4.