Question

To make a benzene soluble cement, $60$ g rosin is melted in an iron pot and $68$ g beeswax and $12$ g shellac are added. How much of shellac should be taken to make $35$ g cement?

Answer 1

Total mass of benzene soluble cement is $60$ g rosing + $68$ g beeswax + $12$ g shellac $=140g$.

However, $35$ g of cement is to be prepared.

Weight of shellac required to prepare $35$ g of cement is $=\left(35g\right)\times \left(\frac{12g}{140g}\right)$$=3g$ of shellac.

Thus, $3$ g of of shellac should be taken to make $35$ g cement.