Stan makes a playlist for the next time he goes running. He has 10 3-minute songs and 15 2-minute songs on his playlist. His entire run takes 100 minutes. If Stan wants a playlist to cover his entire run, how many more minutes of songs will he need in his playlist? Let's answer step by step:
His playlist currently has a playtime of 10 songs * 3 minutes = 30 minutes from 3 - minute songs. It also has a playtime of 15 songs * 2 minutes = 30 minutes from 2 - minute songs. So far, his playlist lasts for 30 + 30 = 60 minutes. He therefore still needs 100 minutes for his run 60 minutes current playtime = 40 minutes. The answer: 40.