Question

HELP PLEASE
A car is traveling at a speed of 81 miles per hour. What is the car's speed in feet per second? How many feet will the car travel in
15 seconds? In your computations, use the fact that 1 mile is equal to 5280 feet. Do not round your answers.
speed ft/s:
distance traveled in 15 seconds ft:

Answer 1

How Many minutes are in an hour? How many Seconds are in an hour?

Answer 2

60 and 3600

Answer 3

3600/18 = ?

Answer 4

Let me see your options as well. Is this multiple choice?

Answer 5

no its free response

Answer 6

okay like she said what is 3600 divided by 18=?

Answer 7

200

Answer 8

look im very sorry but i have a dear friends that would love to help i have school
in the morning @zepdrix trust me he is smarter then me and btw he dosent like ppl who just want the answer soo work for it im sorry @zepdrix will help

Answer 9

\[\large\rm \frac{81miles}{hour}\]So umm :) what were you doing?
Going from hours to minutes?
Then minutes to seconds I guess? :D

Answer 10

81/over?

Answer 11

\[\large\rm \frac{81miles}{hour}\cdot\frac{1hour}{60minutes}\]We would like hours to cancel out, so we make sure it's in the top for this new conversion.

This is a unit, 1hour is equivalent to 60 minutes.
So we're allowed to do this.

Answer 12

What's up? :)
Is that confusing why the 81 is in the numerator?

Answer 13

yes it is

Answer 14

No no no, let's leave it in the numerator :D
It'll get confusing otherwise.

Answer 15

The 81 is the `number of miles` for every hour traveled.
The number is connected to the numerator.

Answer 16

Try to make your peace with it XD lol

Answer 17

okay i got that part

Answer 18

This is where we want to apply "cross cancellation".
We have hours in our numerator AND denominator,
so the units will cancel out.\[\large\rm \frac{81miles}{\cancel{hour}}\cdot\frac{\cancel{hour}}{60minutes}\]

Answer 19

27/20?

Answer 20

Oh simplifying?
Sure sure sure :)\[\large\rm \frac{27miles}{20minutes}\]We want to go from minutes to seconds.

Again, since our minutes are in the `denominator`,
we would like the minutes to show up in the `numerator` of our unit fraction,

Answer 21

\[\large\rm \frac{27miles}{20minutes}\cdot \frac{1minute}{60seconds}\]

Answer 22

\[\large\rm \frac{27miles}{20\cancel{minutes}}\cdot \frac{1\cancel{minute}}{60seconds}\]

Answer 23

\[\large\rm \frac{27miles}{20\cdot60seconds}\]

Answer 24

cross multiply?

Answer 25

With fractions, we always multiply `straight across`.
You can cross-multiply when there is an equality sign between them.
But there is no equals sign here,
so try to get cross-multiply out of your head ^^

Answer 26

9/400?

Answer 27

\[\large\rm \frac{9miles}{400seconds}\]Ok great.
Notice our denominator is perfect now.

We're trying to get to `feet` / `second`
We have the seconds for our units in the bottom.

Answer 28

Now we'll convert `miles` to `feet` using the conversion factor that they gave us:
1mile = 5280feet

Answer 29

Notice that miles is in the numerator,
so for our conversion fraction, we want to put miles in the denominator so we can get the cancellation we're looking for.\[\large\rm \frac{9miles}{400seconds}\cdot\frac{5280feet}{1mile}\]

Answer 30

so cancel this?

Answer 31

Yes, cancel "miles",
and then let's see if we can simplify anywhere.

Answer 32

\[\large\rm \frac{9\cancel{miles}}{400seconds}\cdot\frac{5280feet}{1\cancel{mile}}\]

Answer 33

594/5

Answer 34

?

Answer 35

Ok great.
So we have \(\large\rm \dfrac{594feet}{5seconds}\)

594 feet in 5 seconds.
Another way we can write this (which will look better for your answer):
\(\large\rm \dfrac{594}{5}\dfrac{feet}{sec}\)

(594/5) feet per second.

Answer 36

So there is our speed :)
594/5 ft/s

Answer 37

This is the distance traveled EVERY SECOND.
So if we want the distance traveled in 15 seconds,
we want 15 of these fractions.

So we simply multiply our speed by (15 seconds)

Answer 38

294/5 *15

Answer 39

\[\large\rm \dfrac{594feet}{5seconds}\cdot 15seconds\]Think of these new seconds as being in the "numerator",
so again we have cancellation.\[\large\rm \dfrac{594feet}{5\cancel{seconds}}\cdot 15\cancel{seconds}\]Good, yes.
And make sure you put the 15 in the numerator,
or in other words, multiply the 15 and 294,
he doesn't go in the bottom.

Answer 40

woops it was a 594 right? :)
Not 294 hehe

Answer 41

yes it was ;)

Answer 42

And then ya,
simplify if you're able.

Answer 43

198?

Answer 44

Hmm that seems way too small :o

Answer 45

15 * 594 / 5 = ?

Answer 46

1782?

Answer 47

am i right ?

Answer 48

1782 feet.

Yes good job \c:/

Answer 49

thank you so much @zepdrix