Question

Suppose that four times the square of a number equals 20 times that number. What is the number?

Answer 1

Let the number be k

Four times the square of the number is

`4* k^2`

Twenty times the number is

`20* k=20k`

Since, four times the square of the number is equal to twenty times the number

It can be illustrated as

`4k^2=20k`

Solving the equation above

`\begin{gathered} 4k^2=20k \\ 4k^2-20k=0 \\ 4k(k-5)=0 \\ \text{Divide both sides by 4k} \\ (k-5)=0 \\ k=5 \\ 4k=0 \\ k=0 \\ k=0\text{ or 5} \end{gathered}`

Hence, the number, k, is 0 or 5