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# help plz

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The altitude a (in feet) of a plane t minutes after liftoff is given by a=3400t+600. How many minutes after liftoff is the plane at an altitude of 21,000 feet?

Guest Aug 31, 2017
edited by Guest  Aug 31, 2017

#1
+353
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So I guess time is in minutes.

The question says: How many minutes after liftoff is the plane at an altitude of 21,000 feet?

So... in the equation a=3400t+600, we plug in 21,000 for a. Because we have to find 't' when 'a' is 21,000.

That gives us 21,000 = 3400t+600.

Subtract 600 to both sides to get 20,400 = 3400t

Divide both sides by 3,400 and you get 6 = t.

So it takes 6 minutes for the plane to be at an altitude of 21,000.

6 minutes.

Gh0sty15  Aug 31, 2017
Sort:

#1
+353
+1

So I guess time is in minutes.

The question says: How many minutes after liftoff is the plane at an altitude of 21,000 feet?

So... in the equation a=3400t+600, we plug in 21,000 for a. Because we have to find 't' when 'a' is 21,000.

That gives us 21,000 = 3400t+600.

Subtract 600 to both sides to get 20,400 = 3400t

Divide both sides by 3,400 and you get 6 = t.

So it takes 6 minutes for the plane to be at an altitude of 21,000.

6 minutes.

Gh0sty15  Aug 31, 2017
#2
+76196
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Excellent, Gh0sty....!!!!!!

CPhill  Aug 31, 2017

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