EXPLANATION
Let's see the facts:
Buy price = $40
Sell price = $70
The markup percentage formula is:
[tex]\text{Markup\%}=\frac{Sell\text{ price - cost}}{\cos t}\cdot100[/tex]Substituting terms:
[tex]\text{Markup\% = }\frac{70-40}{40}\cdot100\text{ = 75\%}[/tex]The markup is 75%.