Answer:
Time: 8 minutes
Altitude: 20000ft
Method 1 is easiest
Method 3 is easiest
Step-by-step explanation:
Given
Airplane 1:


Airplane 2:

Required
Determine when both planes would be at the same altitude?
Let the minute be represented by m
For Airplane 1, Its altitude at any height h is:

<em>It is minus (-) because the airplane is descending</em>


For Airplane 2, Its altitude at any height h is:



Method 1:
For both heights to be equal, we have that:

This gives:

Collect Like Terms





<em>Hence, the time they will be at the same altitude is 8 minutes</em>
Substitute 8 for m in



<em>Hence, they will be at the same altitude at 20000ft</em>
Method 2:
We have that:


Since they are to be at the same altitude, then
The difference in their altitude must be 0
i.e.

This gives


Collect Like Terms



Substitute 8 for m in




Method 3:
We have that:


Since they are to be at the same altitude, then
The ratio of their altitudes must be 1
i.e.


Cross Multiply


Collect Like Terms





Substitute 8 for m in




Hence;
<em>Their altitudes must be 20000ft</em>
<em>Though the three methods applied uses the same logic at some point, the first method applied is still the easiest and it is a straight forward method that could be applied in solving the question.</em>
<em>Method 3 is the most difficult.</em>