Did i do this correctly?????

Question

on a weekend trip, you average 35 mph in the city and 60mph on the highway. if the 150 mile trip took 3 hours how much of the time were you driving in the city? I DID THIS ALREADY AND MY ANSWER WAS 1 HOUR..IS THAT RIGHT??

i did 35+60 =95 so then 150-95=55 then i was like okay if the highway took 60mph and it was 55 left then it would just go to the highway so only 1 hour was spent on the city. RIGHT OR WRONG??

I DIDNT DO THIS ONE...BECAUSE I DONT KNOW HOW..HELP?

and on august 15th 1995 the concorde flew 35,035 miles from new york city to new york city in 31 hours 27 minutes. what was the average speed?

Answer 1

1)right

2)1887 minutes.

35035/1887=18.57 minutes.

Answer 2

The basic formula u need, which you already know, is:

speed = distance / time, or

distance = speed * time

If you spend 'x' hours in they city, then you must have spent (3 - x) hours on the highway.  In that case, the formula for the total distance covered is:

distance = (speed in city) x (time in city) + (speed on highway) x (time on highway) = 150

35 * x + 60 * ( 3 - x) = 150

35x + 180 - 60x = 150

-25x = -30

x = 30 / 25 = 1.2 hours = 1 hr 12 mins

Checking:

1.2 * 35 + (3 - 1.2) * 60 = 42 + 108 = 150 miles

You can just add 35 and 60 together to get 95.  You could only do that if you knew that you were driving at both speeds for the same amount of time.  And you don't know that - this is the thing that you are trying to find out!

2. This is even easier.

You do have to work out the time in hours; hours and minutes don't work well in a division.  Luckily this is simple:

31 hours 27 minutes = (31 + 27/60) hours = 31.45 hours

speed = distance / time = 35,035 / 31.45

= 1114 mph.

Is the distance really 35,035?  The earth is only about 25,000 miles around at the widest point.