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)