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A paper airplane thrown off a balcony 60 feet above the ground descends

at a rate of 2 feet per second.
Select the inequality that represents the time, x, when the airplane will be
less than 6 feet above the ground.
A.-2x + 60 < 6
B.2x + 60 < 6
C.-2x + 60 > 6
D. -60x + 2 <6

1 Answer

4 votes

Answer:

The correct option is A

A) -2x + 60 < 6

Explanation:

We know that a paper airplane is thrown at a height of 60 feet.

We can consider 60 feet as the maximum height

Then the paper airplane decends at at rate of 2 feet/seconds

Which means that:

In 1 second, it decends 2 feet

In 2 seconds, it decends 4 feet

In 3 seconds, it decends 6 feet

As the descending of plane is always 2 time the time, we can write the function for descending as

Descended height (feet) = 2x

As the plane is descending continuously, we can find the height at each seconds. For that, we'll have to subtract the descended height from the maximum height.

New height (feet) = Max height - descended height = 60 - 2x

This will give us the New height at any time 't'

Given the condition in question, we have to find the equation for which the New height becomes less than 6, so the equation becomes:

60 - 2x < 6

or rearrange

-2x + 60 < 6

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