Real-Life Math -- Solution
First, the basic problems:
Answer 1:
400 mph
+ 100 mph = 500 mph ground speed
Answer 2:
400 mph -
100 mph = 300 mph ground speed
Answer 3:
Time = 1,000
miles / 300 mph
Time = 3.33 hours
Convert 0.33 hours to minutes.
Minutes
= 0.33 hours x 60 minutes per hour
Minutes = 19.8
The answer is
3 hours, 19.8 minutes.
Now, the main problem. In reality, the ascent
and descent are slower than the 300 mph ground speed. However, for this example
we will pretend each part is equal.
Miles to ascend:
Ascent
= 80 miles / 300 mph
Ascent = 0.27 hours
Minutes = 0.27 hours x 60
minutes per hour
Minutes = 16.2
Miles in straight line flight:
Straight
line = (250 miles total - 80 miles for ascent - 90 miles for descent) / 300
mph
Straight line = 80 miles / 300 mph
Straight line = 0.27 hours
Minutes
= 0.27 hours x 60 minutes per hour
Minutes = 16.2
Miles to descend:
Descent
= 90 miles / 300 mph
Descent = 0.30 hours
Minutes = 0.30 hours x
60 minutes per hour
Minutes = 18
Add the ascent and
straight travel time to find out when you have to start your descent:
16.2
+ 16.2 = 32.4 minutes
You will need to begin your descent 32 minutes
into the flight.
"I'm not exactly a mathematician by any means, but
you definitely need to be able to do quick mental math," says pilot Chris
Siderwicz.
"[Another] example is if you're going somewhere and you
go up to an altitude and you need to descend from your altitude to the airport.
You figure out how many miles away you are and how many feet per minute you
need to descend at. You don't want to be too high when you get there. [Calculations]
like that you need to do quickly."