Lollipop sales calculation

On Friday morning, we opened another box of lollipops, and by lunch, we sold a third of them at 4 crowns each. After lunch, we sold the rest of the box and raised the price to CZK 5 per piece. If there are 90 lollipops in the whole box, how much did we spend on it?

Final Answer:

x =  420 Kc

Step-by-step explanation:

$$\begin{gathered} n=90 \\ a=4\cdot \frac{n}{3}=4\cdot \frac{90}{3}=\frac{4\cdot 90}{3}=\frac{360}{3}=120\text{Kc} \\ b=5\cdot (n-\frac{n}{3})=5\cdot (90-\frac{90}{3})=300\text{Kc} \\ x=a+b=120+300=420\text{Kc} \end{gathered}$$

Try another example