Question

Ellen works for a high-speed rail company that wants to develop a new rail line. Ellen’s project is to find a train that is the second fastest in the world. The Shinkansen Bullet Train in Japan is reported to go as fast as 320 kilometers per hour. The TGV train in France can reach speeds of 89.44 meters per second. Explain to Ellen how to find what speed her new train must go to be the second fastest in this group. Then, find an appropriate speed for Ellen’s train in miles per hour and use the formula distance = speed • time to find how far the train can go in 2.5 hours. Use complete sentences

Answer 1

@jdoe0001 @amistre64 @Luigi0210

Answer 2

@ganeshie8

Answer 3

can i help

Answer 4

Sure i been up for 4 hours stuck on this question.

Answer 5

really

Answer 6

yup well altogther today 2 hours yesterday 2 aswell so equal up to 4

Answer 7

Bullet Train = 320 km / hour

TGV train = 89.44 meters / second = 89.44 X 3600 meters / hour = 89.44 X 3600 /1000 km/ hour

= 89.44 X 3.6 = 321.984 km/ hour

TGV train is faster

Ellen's train has to go faster than 320 km/ hour but less than 321.984 km/ hour i.e around 321 km/ hour to be the second fastest train ANSWER

Distance in 2.5 hours = 321 X 2.5 = 802.5 km ANSWER

Answer 8

really yahoo answers

Answer 9

come on that is easier dude

Answer 10

Well how am i suppose to put that in complete sentences??

Answer 11

nvm

Answer 12

okay atleast i gave u and answer

Answer 13

Btw this is 9th grade ur prob in 6th or 7th grade

Answer 14

i am in 8 th

Answer 15

@phi @whpalmer4 @mathslover

Answer 16

what part of the problem confuses you?

you are given the speed of the
TGV train is 89.44 meters per second.

convert that to km/hour

Answer 17

what did i had to convert and wanted to know if i had to multiply or divide

Answer 18

to convert units, you start by writing down that you have
\[ \frac{meters}{second}\]
you want \[ \frac{km}{hour} \]
you need "conversion factors" to multiply the first fraction by to get the second fraction

if we look just at the units, to change meters to km we want to multiply by
\[ meters \cdot \frac{km}{meters} \]
the idea is that the meters "cancel"

so you need a factor of km per meter
if you know 1000 meters per km or \( 1000 \frac{meters}{km}\)
that is "upside down". if we flip it we get
\[ \frac{1}{1000} \frac{km}{meter} \]

Answer 19

does that part make any sense?

Answer 20

Now i se how you are at 99 lol yea it make alot of sense

Answer 21

so far we have
\[ 89.44 \frac{\cancel{meters}}{sec} \cdot \frac{1}{1000} \frac{km}{\cancel{meters}}= \frac{89.44}{1000} \frac{km}{sec} \]

Answer 22

So its 89.44 seconds x 1/1000km=89.44/1000 km/sec

Answer 23

89.44 meters/second * 1/1000 km/meter
the meters cancel (divide out) and leave km/sec

Answer 24

O ok

Answer 25

we want to change seconds to hours
60 seconds = 1 minute
60 minute = 1 hour
60*60 seconds = 1 hour
3600 seconds = 1 hour
we have 1 hour per 3600 seconds
\[\frac{1 \text{ hour}}{3600 \text{ sec}} = \frac{1}{3600} \frac{hour}{sec}\]

Answer 26

Oh ok

Answer 27

your problem is (so far)
\[ \frac{89.44}{1000} \frac{km}{sec} \]
if you want to "cancel" the secs what should we multiply by ? hour/sec or sec/hour ?

Answer 28

sec/hour?

Answer 29

yes, because sec "up top" will cancel the sec "down below"

we know the conversion factor
\[ \frac{1}{3600} \frac{hour}{sec} \]
but that is upside down. Flip it to
\[ 3600 \frac{sec}{hour} \]
multiply your problem by that factor

Answer 30

btw 1/3600 flipped is 3600/1 but when we divide by 1, we don't bother to write it. we just write 3600

Answer 31

So we have 3600 is how far the train can go in 2.5 seconds?

Answer 32

no. what we know is there is 3600 seconds per hour

the "conversion factor" for seconds/ hour is 3600
we use the conversion factor.
\[ \frac{89.44}{1000} \frac{km}{sec} \cdot 3600 \frac{sec}{hour} \]

Answer 33

Ok so distance = speed • time
the distance would be not yet found
But the spped is about to be but the time is 89.44/1000 km/sec * sec/hour

Answer 34

But the spped is about to be but the time is 89.44/1000 km/sec * sec/hour

can you say that more clearly ?

Answer 35

Ok what im saying that distance is not yet solved but the speed is about to turn into time

Answer 36

we have been working on only one thing:

change speed measured in meters per second to speed measured in kilometers per hour
we will still have speed, but different units.
the final step in this "conversion" is to simplify this expression
\[ \frac{89.44}{1000} \frac{km}{sec} \cdot 3600 \frac{sec}{hour} \]

Answer 37

O ok

Answer 38

notice you don't just multiply by sec/hour. you need to multiply by a conversion factor (number) that has units of sec/hour. we know that
3600 sec per hour or 3600 sec/hour is the factor

Answer 39

Ok i understand that now

Answer 40

what do you get after simplifying
\[ \frac{89.44}{1000} \frac{km}{sec} \cdot 3600 \frac{sec}{hour} \]?

Answer 41

268.32

Answer 42

your calculator is broken. try again

Answer 43

lol ok

Answer 44

321.984??

Answer 45

yes. but with these problems *always* include the units
can you do that ?

Answer 46

I can try nothing like putting effort in anything

Answer 47

\[ \frac{89.44}{1000} \frac{km}{sec} \cdot 3600 \frac{sec}{hour} = 321.984 \frac{km}{sec} \cdot \frac{sec}{hour} \]
simplify the units (by noticing that sec/sec = 1)

Answer 48

O ok

Answer 49

What about km is that what i have to figure out?

Answer 50

first, simplify
\[ 321.984 \frac{km}{sec} \cdot \frac{sec}{hour} \]

Answer 51

sec/hour= 1 km/sec=

Answer 52

Here is the rule: if you have the *same thing* in the top and bottom, you can erase both

Answer 53

ok

Answer 54

do you see "sec" is up top and down below? that means you can erase both of them
what is left over ?

Answer 55

Km/sec

Answer 56

no. you erase sec from the top
and you erase sec from the bottom
what is left in\[ 321.984 \frac{km}{sec} \cdot \frac{sec}{hour} \]

Answer 57

*Km/hour

Answer 58

yes, we have the speed is
321.984 km/hr

Answer 59

Wow

Answer 60

now for the rest of the question


TGV train speed is 321.984 km/hr
Shinkansen Bullet Train 320 km/hr

you want a train that is second fastest (slower than TGV and faster than Shinkansen)

Answer 61

that means pick a speed between those two numbers

Answer 62

Ok

Answer 63

TGV train speed is 321.984 km/hr

Answer 64

yes
but we need to answer
what speed her new train must go to be the second fastest in this group.

Answer 65

Ellen is building a new train. She wants it to be slower than TGV but faster than the other

Answer 66

It need to go 321.000

Answer 67

yes, that is the easiest speed to pick. but it could go lots of different speeds: 321.1
or 321.123 or 320.5 or.... There are an infinite number of speeds it could be. but 321 is definitely the "nicest" number we can pick.

Answer 68

Last part of the question

distance = speed • time
in 2.5 hours at speed = 321 km/hour

Answer 69

you should put the numbers and the units into the equation
(be sure to include the units)

Answer 70

Distance= speed * time
= 321.00km/hour

Answer 71

you need to include * time
time is 2.5 hours

Answer 72

oh yea i meant to add that i forgot i knew i forgot something

Distance= speed x time
=321.00km/hour x 2.5hours

Answer 73

ok, that looks good. you have
\[ Distance = 321.00 \frac{km}{hour} \cdot 2.5 \text{ hour} \]
or
\[ Distance = 321.00 \cdot 2.5 \frac{km}{hour} \cdot \text{ hour} \]

simplify the units
Here is the rule: if you have the *same thing* in the top and bottom, you can erase both

Answer 74

remember that hour is the same as hour/1
so the "hour" is up top.

Answer 75

The first 1.

Answer 76

\[ Distance = 321.00 \cdot 2.5 \frac{km}{hour} \cdot \frac{ hour} {1}\]
simplify the units
Here is the rule: if you have the *same thing* in the top and bottom, you can erase both

Answer 77

804.960

Answer 78

First simplify the units

Answer 79

km/hour
km/1

Answer 80

i did with the 1/km cuz i took out the hour and turned it into 1

Answer 81

Here is the rule: if you have the *same thing* in the top and bottom, you can erase both
\[ Distance = 321.00 \cdot 2.5 \frac{km}{\cancel{hour}} \cdot \frac{\cancel{\text{ hour}}}{1} \]
like that. we don't need to show the 1 (divide by 1 is not usually written down)
so we get
\[ Distance = 321.00 \cdot 2.5\ km \]

Answer 82

Oh yea my bad i was going to erase the 1 and hour sense thats a part of an hour now i understand that

Answer 83

now multiply 321 * 2.5
be careful.

Answer 84

80.25

Answer 85

????

Answer 86

no. First, always write down the units (the km) or you might forget
second, 321 * 2.5 will be bigger than 321 (so it can't be 80 !)

Answer 87

oh ok

Answer 88

802.5?

Answer 89

yes, but with the units

Answer 90

802.5km

Answer 91

yes.

Answer 92

to finish this
Explain to Ellen how to find what speed her new train must go to be the second fastest in this group.

the answer is change the speed in m/sec to km/hr
You can look up above to see how we did that.
then compare the speed of the two trains and pick a speed in between the two trains' speeds

finally, show the work to find the distance traveled by Ellen's train going at 321 km/hr for 2.5 hours

Answer 93

Wait wat that a little confusing @phi

Answer 94

Ellen's train must go 802.5km

Answer 95

to be the second fastest

Answer 96

Ellen's train goes 802.5 km in 2.5 hours. That is a distance.
But the question first asks
Explain to Ellen how to find what speed

speed is km/hour (speed is how fast you move)

Answer 97

ok