Question

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?

Answer 1

Answer:

6 minutes

Step-by-step explanation:

We are given that an altitude a (in feet) of a  plane t minutes after liftoff is given by

$a=3400 t+600$

We have to find that how many minute after liftoff is the plane at an altitude of 21,000 feet.

$a=3400 t+600$

$3400 t=a-600$

Using subtraction property of equality

$t=\frac{a-600}{3400}$

Substitute the value of a then we get

$t=\frac{21000-600}{3400}$

$t=6$ minutes

Hence,  6 minutes after liftoff is the plane at an altitude of 21,000 feet.

Answer 2

21000 = 3400 t + 600 -> 21000 - 600 = 3400 t --> 20400 = 3400 t --> 20400/3400 = t --> t = 6  min