Grady rides his bike 60% faster than his little brother Noah. If Grady rides 15 miles further than Noah in three hours, how fast in miles per hour does Noah ride?
Let Noah's pace in mph = N
Let the distance he rides in 3 hrs = D
So 3N = D
And
Noah's pace * 1.6 = Grady's pace
So
Grady's pace * time = D + 15
(N * 1.6 ) * 3 = D + 15
4.8 N = D + 15
4.8N = 3N + 15
4.8N - 3N = 15
1.8N = 15
N = 15 / 1.8 = 8.33 mph = Noah's pace
