The directions for mixing an insect spray say to use 1 1 three fourths 3 4 ounces of chemical in each gallon of water. how many ounces of chemical should be mixed with 5 5 two fifths 2 5 gallons of water? first, estimate the answer to the application problem

1 3/4 oz is mixed with 1 gallon of water.  With 5 2/5 gallons of water, since we multiplied the number of gallons by 5 2/5, we multiply the amount of chemical by 5 2/5 as well:
1 3/4 * 5 2/5
Convert to improper fractions:
7/4 * 27/5 (because 1*4+3=7 and 5*5+2=27)
189/20 = 9 9/20 (because 20 goes into 189 9 times with 9 left over)