Question

Joseph needs to drive 42 miles. They were going to drive at a certain average speed, but if they drive 10 mph faster, the trip will take 6 minutes (1/10 of an hour) less time. How fast were they going to drive? Write out the equation(s) ​

Answer 1

The speed is 60 mph.

Explanation:

distance = 42 miles

Let he drove with speed v and time is t.

distance = speed x time

42 = v t ..... (1)

42 = (v + 10)(t - 1/10) ..... (2)

`42 = 42 -(v)/(10)+ 10 t - 1\\\\t =(10+v)/(100)\\\\Put in (1)\\\\42 = (v(10+v))/(100)\\\\v^2 + 10 v - 4200 = 0 \\\\v = (-10\pm √(100+4* 4200))/(2)\\\\v =(- 10 \pm 130)/(2)\\\\v =- 70 mph, 60mph`

So, the speed cannot be negative so the speed is 60 mph.