2020 · Q18
If x men working x hours per day can do x units of work in x days, then y men working y hours per day in y days would be able to do k units of work. What is the value of k?
Elementary MathematicsTime and Work
- Ax²y⁻³
- Bx³y⁻²
- Cy²x⁻³
- Dy³x⁻²
Explanation
x^3 man-hours produce x units, so one unit costs x^2 man-hours; y^3 man-hours therefore produce y^3/x^2 units. So k = y^3*x^-2 - option (D). Dimensionally k must scale as y^3/x^2, which only option (D) satisfies.