Question

Lauren is at a friend's home that is several miles from her home. She starts walking at a constant rate in a straight line toward her home. The expression −2t + 10 gives the distance, in miles, that Lauren is from her home after t hours. Answer the following questions using the information above.
a. How many miles away from her house did Lauren start?
b. How fast is Lauren moving towards her house?
c. Why is the rate negative?
d. How far away from her house is Lauren after 4 hours?

Answer 1

a.

Lauren was 10 miles away from her house when he started.

Since the expression for Lauren's distance from her house, d = -2t + 10, to determine the number of miles away from his house that Lauren starts, we input t = 0, since this is the time Lauren starts walking.

So, with t = 0, d = -2t + 10

= -2(0) + 10

= 0 + 10

= 10 miles.

So, Lauren was 10 miles away from her house when he started.

b.

Lauren was moving at a rate of -2 mph towards her house.

To find how fast Lauren was moving towards her house, we differentiate d with respect to t.

So, dd/dt = d(-2t + 10)/dt

= d(-2t)/dt + d(10)/dt

= -2 + 0

= -2 mph

So, Lauren was moving at a rate of -2 mph towards her house.

c.

The rate is negative because her distance towards her house is decreasing

The rate is negative because her distance towards her house is decreasing since she is moving towards her house.

d.

Lauren is 2 miles away from her house after 4 hours

To find this, we input t = 4 into the equation for d.

So, d = -2t + 10

= -2(4) + 10

= -8 + 10

= 2 miles.

So, Lauren is 2 miles away from her house after 4 hours

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