Question

Solve the following problems by writing a problem8 is 40% of what number?

Answer 1

Give to the number the letter x, then the 40% of x is 8:

`x\cdot(40)/(100)=8`

Solve the equation for x:

Multiply both sides of the equation by 100:

`\begin{gathered} x\cdot(40)/(100)\cdot100=8\cdot100 \\ \\ x\cdot40=800 \end{gathered}`

Divide both sides of the equations into 40:

`\begin{gathered} x\cdot(40)/(40)=(800)/(40) \\ \\ x=20 \end{gathered}`

Then, 8 is the 40% of 20