When brakes are applied to a bus the deceleration produced is 25cm/s^2 and the bus takes 20s to stop calculate the distance travelled by the bus during this time

The answer is 5000cm. This is because of what cm/s^2 means. 25cm/s^2 means you are travelling 25cm per second. So for every one second, you travel 25cm. However, you are travelling for 20 seconds, not 1, so you need to multiply. So if for every one second you are travelling 25cm, then in two seconds, you would travel 50, and you should keep adding 25 until you’ve done that 20 times. However, we have a much simpler way of doing that. Just multiply. So 25x20=5000. Remembering your units, that’s 5000cm. Hope this helps!