Answer :
22.5 miles long
basically all you have to do is count out the factors until you reach two number of 45 apart
DIFFERENCE
7MPH 5MPH BETWEEN THEM
7 5 2
14 10 4
21 15 6
28 20 8
35 25 10
42 30 12
49 35 14
56 40 16
63 45 18
70 50 20
77 55 22
84 60 24
91 65 26
98 70 28
105 75 30
112 80 32
119 85 34
126 90 36
133 95 38
140 100 40
147 105 42
154 110 44
161 115 46
considering the differences are even it means it has to fall in the middle. if you count from the top it is 22.5 numbers down giving you the number of miles.
I'm sure there is an easier way but this is how i would solve it. :)
basically all you have to do is count out the factors until you reach two number of 45 apart
DIFFERENCE
7MPH 5MPH BETWEEN THEM
7 5 2
14 10 4
21 15 6
28 20 8
35 25 10
42 30 12
49 35 14
56 40 16
63 45 18
70 50 20
77 55 22
84 60 24
91 65 26
98 70 28
105 75 30
112 80 32
119 85 34
126 90 36
133 95 38
140 100 40
147 105 42
154 110 44
161 115 46
considering the differences are even it means it has to fall in the middle. if you count from the top it is 22.5 numbers down giving you the number of miles.
I'm sure there is an easier way but this is how i would solve it. :)