A 150 cm ribbon is cut into two pieces so that one piece is four times as long as the other. How long is the shorter piece?

Explanation

1. 01

   Let the shorter piece be $s$ cm; the longer is $4s$ cm.

2. 02

   $s + 4s = 150$, so $5s = 150$.

3. 03

   $s = 30$ cm.