88 seconds.
You are calculating a 20% decrease. This means you need to calculate 20% of 110.
First, calculate 10%, which is much easier. To do this, divide 110 by 10 (because you’re going from 100% to 10%, which is a division by 10, so you need to do the same to the 110)
110/10 = 11
However, now you need to get from 10% to 20%, so multiply by 2.
20% = 22
HOWEVER, YOU’RE NOT DONE HERE.
I know too many people who make the mistake in an exam of stopping here, myself included.
You’re working out a decrease! This is only the amount it has decreased by, not the final time.
To calculate the final time, you need to minus our value from the average.
So, 110-22 = 88
Therefore, it takes cashier A 88 seconds!
Hope this helps :)
