Calculate the amount of 90% pure chemical to add to 460 litres to obtain a 78% pure mixture.

Here's the solution for Item 4:

Item 4:

a)
The problem asks to calculate the amount of 90% pure chemical to add to 460 litres to obtain a 78% pure mixture. The purity of the initial 460 litres is not explicitly stated in the problem. This information is crucial for a unique solution.

However, in typical mixing problems of this nature, if a target purity (78%) is between the purity of one component (90%) and an unstated component, the unstated component's purity must be lower than the target purity. A common assumption in such cases, if not specified, is that the unstated component is either 0% pure (a