The <em><u>correct answers</u></em> are:
A) 60 miles; and B) 3.375 hours.
Explanation:
We will use the equation d = rt for this.
For the first leg of the trip, the bird travels 20 miles per hour for x hours. This gives us the equation
d = 20x
For the return trip, the bird travels 4 miles per hour slower, so 20-4 = 16 miles per hour. He also travels 6 miles less than the return distance, for x hours:
d-6 = 16x
To isolate d, we will add 6 to each side:
d-6+6 = 16x+6
d = 16x+6
We will set the two equations equal to one another, since they both equal d:
20x = 16x+6
Subtract 16x from each side:
20x-16x = 16x+6-16x
4x = 6
Divide both sides by 4:
4x/4 = 6/4
x = 1.5
He travels for 1.5 hours both times.
The first time, 1.5 hours at 20 miles per hour is:
d = 1.5(20) = 30 miles
The original trip is 30 miles. This makes the entire trip 30(2) = 60 miles.
On the return trip, he travels 30-6 = 24 miles at 16 miles per hour:
24 = 16x
Divide both sides by 16:
24/16 = 16x/16
1.5 = x
If he goes 24 miles in 1.5 hours at 16 miles per hour, we can use a proportion to find the time it takes for the entire return trip:
24/1.5 = 30/x
Cross multiplying,
24*x = 1.5(30)
24x = 45
24x/24 = 45/24
x = 1.875
This gives him a total time of 1.5+1.875 = 3.375 hours.
