Question

Sanford can assemble a computer in 60 minutes. Colleen can assemble a computer in 40 minutes. If they work together, how many minutes does it take them to assemble a computer? 5 minutes 6 minutes 20 minutes 24 minutes

Answer 1

$\dfrac{1}{60}+\dfrac{1}{40}=\dfrac{1}{x}\\ \dfrac{2}{120}+\dfrac{3}{120}=\dfrac{1}{x}\\ \dfrac{5}{120}=\dfrac{1}{x}\\ 5x=120\\ x=24$