Question

The formula d = t² + 5 t expresses a car's distance (in feet) from a stop sign, d, in terms of the number of seconds t since it started moving.
Determine the car's average speed over the interval of time from t = 4 seconds to t = 7 seconds.

Answer 1

Answer:

The car's average speed is 16 feet per second.

Explanation:

The expression for the average speed is as follows;

$A.S=\frac{\textrm{Total distance}}{\textrm{total time}}$

Given expression of distance:

$d=t^{2}+5t$

Put t= 4 s.

$d(4)=(4)^{2}+5(4)$

d(4)= 36 ft

Put t= 7 s in the given expression.

$d(7)=(7)^{2}+5(7)$

d(7)= 84 ft

Calculate the car's average speed over the interval of time from t = 4 seconds to t = 7 seconds.

$A.S=\frac{d(7)-d(4)}{7-4}$

$A.S=\frac{84-36}{7-4}$

A.S= 16 feet per second

Therefore, the car's average speed is 16 feet per second.