Answer: 21 1/4 bags
Step-by-step explanation: If Hank used 4 1/4 bags of seed to plant the grass in his front yard and then used 5 times as much to plant the back yard he used a total of 21 1/4 bags.
This is calculated by multiplying 4 1/4 x 5 = 20 5/4, which equals 21 1/4.