Question 210101
Whenever you are working a problem in which you want to know the speed, distance or time a vehicle travels, you will most likely start with the basic formula {{{d=rt}}} where 'd' is the distance traveled, 'r' is the rate/speed of the vehicle or person, and 't' is the time taken to travel.


In plain English, the distance traveled is equal to the speed multiplied by the time.


Ex: I travel 50 mph and I drive for 2 hours. How far have I gone? I've gone 100 miles (you might have done this in your head). Simply multiply 50 by 2 to get 100. 

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{{{d=rt}}} Start with the given formula



{{{15=35t}}} Plug in {{{d=15}}} (since he needs to travel 15 mi) and {{{r=35}}} (his speed in miles per hour)



{{{15/35=t}}} Divide both sides by 35 to isolate 't'. Since we want to know the time, we want to get 't' all by itself.



{{{(5*3)/(5*7)=t}}} Factor 15 to get 5*3 and 35 to get 5*7



{{{(cross(5)*3)/(cross(5)*7)=t}}} Cancel out the common factors.



{{{3/7=t}}} Simplify



So the answer is {{{t=3/7}}}. This means that he'll travel for {{{3/7}}} of an hour. What does this mean? Well, if we find the decimal equivalent of {{{3/7}}} with a calculator, we get {{{3/7=0.4286}}} (approximately). Now multiply this value by 60 (to convert the time to minutes) to get: {{{60*0.4286=25.716}}}



So it takes him roughly 25.716 minutes to go 15 miles at 35 mph.