Question 793928
8 hours, 45 minutes = 8 hr + 45 min


8 hours, 45 minutes = 8 hr + 45/60 hr


8 hours, 45 minutes = 8 hr + 0.75 hr


8 hours, 45 minutes = 8.75 hours


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d = rt


630 = r*8.75


630/8.75 = r


72 = r


r = 72


So you need to travel <font color="red">72 miles per hour</font>


Note: this average speed is unrealistic (even on the highway in most places), so ideally you should plan accordingly and stretch out that time limit.