Jon decides to take up baseball

Jon decides to take up baseball. He can throw a fastball at 80 miles per hour. He goes through intense training 4 times for 4 weeks each time and at the end of the last one he can throw a ball 20% faster. How much speed (in mph) did he gain per week, assuming he gained an equal amount of speed (in mph) each week?

GSM8K — Grade School Math 8K (Cobbe et al., OpenAI, 2021) · train #5214