Question

What is the maximum Truck Bed Height you can successfully load a 5W piano on by 3 friends?

Answer 1

If one friend can perform work $E$, and the weight is $W$, then the height is

$$h=\frac EW.$$

Three equal friends perform three times more work, the weight is 5 times greater, so:

$$h_3=\frac{3E}{5W}=\frac35h=0.6h.$$

The new height is just 60% of the initial.