Question

Help plz,
Set up an equation to solve the following problem, and then solve it.
On a sales trip, Irwin drove 330 miles averaging a certain speed. The return trip was at an average speed that is 11mph faster. Total time for the round trip was 11 hours. Find Irwin’s average speed on each part of the trip.

Answer 1

well, its not hard , what dont we know , what we do we need to find , assign them to variables

Answer 2

Use distance equal rate times time.

Answer 3

let x equal the "certain speed"

Answer 4

so assume 330 miles for one way , that means in total he drove 660miles

Answer 5

we know the total time was 11

but time = distance / speed

time for first section = 330 / x

times for second section = 330/ ( x+11)

so ( 330/x) + [330 / (x+11) = 11

Answer 6

\[\frac{330}{x} + \frac{330}{x+11} =11\]

Answer 7

solve for x

Answer 8

i c. Thanks

Answer 9

it has two solutions x=-6, x=55

but because we are dealling with real world ( and yes, it says "speed", not velocity ) so a negative value is not allowed

Answer 10

so x=55

means for first half average was 55mph, and for second half average was 66mph ( ie 55 +11 )

Answer 11

Actually the average speed for the entire trip was 660/11 or 60 mi.
So wouldn't that made the avg speed for the first part 54.5 mph and the second part 65.5?

Answer 12

dnt think so

Answer 13

The avg of 54.5 + 65.5 is 120/2=60

Answer 14

firstly where did u magically get 54.5 and 65.5 from

Answer 15

x + (x+11) 660
---------- = ----- = 60
2 11

Answer 16

Nothing magic about it.

Answer 17

yes....
and.....?

Answer 18

yes there is , there are alot of different ways to get two numbers to sum to 120 , why did you pick those two numbers? , theres no calculations to suggest why you chose thoise two

Answer 19

ohh I think i see what you are doing now

Answer 20

bit of a dangerous way to think

Answer 21

x= first avg speed (certain speed)
x+11 is the second avg speed (return trip

Their sum divided by 2 equals the total avg speed
660/11 is also the total avg speed. Take it from there

Answer 22

Just sayin your way seems correct just wondering why they dont come out the same. Did you round off or take a root of or whatever/

Answer 23

no, the reason why they dont come out correct is because your way of thinking is wrong :P

Answer 24

Well they came out close.lol
gotta run

Answer 25

:\, the average of a sum is not the sum of the avergaes

Answer 26

Gotcha, I see the error of my logic.