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An object is dropped from a small plane. As the object falls, its distance, d, above the ground after t seconds, is

given by the formula d = -16² +1,000. Which inequality can be used to find the interval of time taken by the object
to reach the height greater than 300 feet above the ground?
-16² +1,000 <300
-16² +1,000 ≤300
-16² +1,000 ≥ 300
-16f²+1,000 > 300

An object is dropped from a small plane. As the object falls, its distance, d, above-example-1
User Dalelane
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1 Answer

6 votes

Answer:

-16²+1,000 > 300 [After an edit in the original expression, as noted below).

Explanation:

The equation d = -16² +1,000 tells us the height above ground, d, of the object after t seconds. When t = 0 seconds, the ball has not been dropped yet, but the equation tells us that d = 1,000 at t = 0. That means the object starts at 1,000 feet above ground.

We want the time it takes for the object to reach any height greater than 300 feet above ground. This is a tad (metric for just a tiny bit) unexpected, since even at time of 0 the object is greater than 1,000 feet.

Looking at the answer options, note that the left side of the inequalities is -16^2+100. I will assume the 4th option has a typo: the f^2. It should read the same as the others.

-16^2+100 is the distance, d. So to help us think this through, let's rephrase the answer options in terms of distance, d:

1) d<300

2) d≤300

3) d≥300

4) d>300

The question asks "We want the time it takes for the object to reach any height greater than 300 feet above ground."

Option 4 says d>300, or height greater than 300. That is the inequality that matches the question. [Note: It did not say greater than or equal to (option 3).]

User Will Abson
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