Question

6. Mary and Steve each travel 845 miles. Mary drove an average of 5 mph faster than Steve and completed the trip in one hour's less time
than Steve. What was each person's average speed?

Answer 1

Answer:

Steve had an average speed of 62.55 mph while Mary had an average speed of 67.55 mph

Step-by-step explanation:

Here, we want to calculate the average speed of each of the two.

From the question, we are told that Mary drove an average of 5 mph faster than steve.

So, let the average speed of Steve be x mph, this means that the average speed of Mary will be (x + 5) mph

Mathematically;

Time = distance/speed

Time taken by Steve = 845/x hours

Time taken by Mary = 845/(x + 5)

But Mary took an hour less to complete her own trip;

This means that;

if we add one hour to the time spent by Mary, then we will have the time spent by Steve

845/(x + 5) + 1 = 845/x

845/(x + 5) = 845/x -1

845/(x + 5) = (845 - x)/x

Cross multiply;

845(x) = (x + 5)(845-x)

845x = x(845-x) + 5(845-x)

845x = 845x-x^2 + 4225 - 5x

x^2 + 5x - 4225 = 0

We can solve this using the quadratic formula;

x = -b ± √(b^2 - 4ac)/2a

where a = 1 , b = 5 , c = -4225

x = -5 ± √(5^2 - 4(1)(-4225)/2(1)

x = -5 ± √(25 + 16,900)/2

x = -5 ± √(16,925)/2

x = (-5 + 130.1)/2 or (-5-130.1)/2

We ignore the negative side as speed cannot be negative

x = (-5 + 130.1)/2 = 62.548 which is approximately 62.55 mph

So steve’s speed is 62.55 mph while Mary’s speed = 62.55 + 5 = 67.55 mph