Mr. williams' physical education class lasts 7/8 hour. how many minutes are not spent on instructions . playing game: 1/2 , instructions: 1/5 ,warm up and cool down: 3/10

First you would find a common denominator. If 40 is the LCM then you would have to add playing games, instruction,warm-up, and cool-down. Then you will subtract the sum from the total class time and bam! You get your answer!

52.5 minute class

1/5 spent on instruction - 20%

Just find 80 percent of 52.5 and you will get 42 minutes not spent on instruction