Answer
The first part will be 18
The second part will be 72
Explanation
To separate 90 into two parts so that one part is four times the other number, we shall perform the following:
Let the first part be x
Let the second part be 4x
So,
[tex]\begin{gathered} x+4x=90 \\ \\ 5x=90 \\ \\ x=\frac{90}{5} \\ \\ x=18 \end{gathered}[/tex]
Therefore, the first part will be 18 and the second part will be (4 x 18) = 72
