Grayson first travels 1 * 25 = <<1*25=25>>25 miles
Then Grayson travels 0.5 * 20 = <<0.5*20=10>>10 miles
Grayson travels a total of 25 + 10 = <<25+10=35>>35 miles
Rudy travels 3 * 10 = <<3*10=30>>30 miles
Grayson travels 35 - 30 = <<35-30=5>>5 miles more than Rudy
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