Answer:
8:30 PM
Step-by-step explanation:
Let's say that x is minutes since 6:20 PM, and y is position in miles.
Since Jonathan drives at a constant rate, the position vs time graph is linear. Two points on the line are (0, 75) and (20, 85). The slope of the line is:
m = Δy / Δx
m = (85 − 75) / (20 − 0)
m = ½
So the equation of the line is:
y = ½ x + 75
We want to find x when y is 140.
140 = ½ x + 75
65 = ½ x
x = 130
So 130 minutes after 6:20 PM is when Jonathan's position will be 140 miles. 130 minutes is 2 hours and 10 minutes. So the time will be 8:30 PM.
