SOLUTION: Could you please help me with this word problem? Problem: In 1927, Charles Lindbergh was the first person to fly nonstop across the Atlantic Ocean. Today, commercial airliners f

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Question 715363: Could you please help me with this word problem?
Problem: In 1927, Charles Lindbergh was the first person to fly nonstop across the Atlantic Ocean. Today, commercial airliners fly from New York to Paris five times as fast, or 400 miles/hour faster than Lindbergh's plane.
a. At what speed did Charles Lindbergh's plane fly?
b. At what speed do commercial airplanes fly today?
c. If it took Lindbergh about 36 hours to cross the Atlantic, what distance did he fly?
d. How long does it take a commercial airplane today to fly across the Atlantic?
(For section a i thought the answer might be 80 mph. I got this by trying out the equation 400/5=80... However, i feel this is incorrect.)
Answer by Edwin McCravy(20064) About Me  (Show Source):
You can put this solution on YOUR website!
a. At what speed did Charles Lindbergh's plane fly?
Let the answer be x mph.

Today, commercial airliners fly from New York to Paris five times as fast, 
Therefore commercial airliners fly 5x mph

or 400 miles/hour faster than Lindbergh's plane.
Therefore commercial airliners also fly x+400 mph.

So 5x mph must equal x+400 mph, so

           5x = x + 400
           4x = 400
            x = 100

So Lindberg flew at 100 mph.

b. At what speed do commercial airplanes fly today? 
5 times as fast as Lindberg, or 5×100 or 500 mph. Or you can say 
400 mph faster then 100 mph or 500 mph.  Either way you get 500 mph.

c. If it took Lindbergh about 36 hours to cross the Atlantic, what
distance did he fly?
Distance = Speed × time = 100×36 = 3600 miles

d. How long does it take a commercial airplane today to fly across
the Atlantic?
TIME = DISTANCE÷SPEED = 3600÷500 = 7.2 hours = 7 hours 12 minutes

You can also get that answer by taking 1%2F5th of 36 hours,
because going 5 times as fast will take only 1%2F5th of the 36
hours that Lindberg took, and 1%2F5th of 36 is also 7.2 hours,
or 7 hours 12 minutes.

Edwin