Question: Mike plays ping pong for 40 minutes.  In the first 20 minutes, he scores 4 points.  In the second 20 minutes, he scores 25% more points.  How many total points did he score?
Answer: 
He scored 4*.25=1 point more in the second 20 minutes
So he scored 4+1=5 points in the second 20 minutes
So in total, he scored 4+5=9 points in the 40 minutes