By what percent will the number change if the number were to be multiplied by 5?

Question

Please help me, this is a very hard question...

Answer 1

A 400% increase in value, if multiplied by 5

5x -x = 4x

4x/x = 4 = 400% change

If gasoline were $2 per gallon and rose to $10 per gallon, that's an $8 increase

8/2 = 4 = 400% increase in price