A and B are two heavy steel blocks. If B is placed on top of A, the weight increases by 60%. How much weight will reduce with respect to the total weight of A and B, if B is removed from the top of A?

Let the weight of block A be $W_A$ and the weight of block B be $W_B$.
When B is placed on top of A, the total weight increases by 60%, which implies that the weight of B is 60% of the weight of A.

$$W_B=\frac{60}{100}{W}_A=\frac{3}{5}{W}_A$$

Let $W_A=5\text{units}$, then $W_B=3\text{units}$.
Total weight of A and B = $5+3=8\text{units}$.
If B is removed, the weight reduces by $3\text{units}$ (the weight of B).
Percentage reduction with respect to the total weight:

$$\text{Percentage reduction}=\frac{3}{8}\times 100\%=37.50\%$$