Gretchen read that you should spend 10 minutes walking for every 90 minutes you spend sitting. If Gretchen spends 6 hours working at her desk, how long will she spend walking? Think carefully first, then make a decision:
First find the total number of minutes Gretchen spends sitting at her desk: 6 hours * 60 minutes / hour = 360 minutes. Then divide this amount by 90 minutes to find how many walking breaks Gretchen takes: 360 minutes / 90 minutes / break = 4 breaks. Then multiply the number of breaks by the length of each break to find how long Gretchen spends walking: 4 breaks * 10 minutes / break = 40 minutes. So, the answer is 40.