Question

The landscaper pours 200 gallons of herbicide in a pond. The herbicide degrades 10% each week. The landscaper will put another dose in the pond when thr herbicide level drops below 50 gallons. In about how many weeks will he need to add more herbicide?

Answer 1

8weeks
10% of 200 is 20if you subtract 20 from 200 then you have to do it 8 times to get below 50
#1) 200-20=180
#2) 180-20=160
#3) 160-20=140
#4) 140-20=120
#5) 120-20=100
#6) 100-20=80
#7) 80-20=60
#8) 60-20=40