To determine the speed of the jet plane, we need to use the formula for speed:
[tex]\[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} \][/tex]
In this problem, the distance the plane traveled is given as 1,400 miles, and the time it took to travel that distance is 3.5 hours. Plugging these values into the formula, we get:
[tex]\[ \text{Speed} = \frac{1400 \text{ miles}}{3.5 \text{ hours}} \][/tex]
To find the speed, divide the distance by the time:
[tex]\[ \text{Speed} = \frac{1400}{3.5} \][/tex]
[tex]\[ \text{Speed} = 400 \text{ miles per hour} \][/tex]
Thus, the speed of the plane is:
[tex]\[ 400 \text{ miles per hour} \][/tex]
So, the correct answer is:
c) 400 miles per hour
