Convert Feet to Foose: Ann & Rachael's Heights

[wakejosh]

If i could get anyone to double check my answers on the following it would be a big help. thanks

On planet Z, the standard unit of length is the foose. Ann the
Astronaut is 5.90 feet tall on
earth. She lands on planet Z and is measure to be 88 foosi
(plural of foose) tall. Her crew
member Rachael is 94 foosi tall. How tall is Rachael in Earth
measurements?

i get 6.3 feet

5.9/88 = 14.92

94/14.92 = 6.3

is this correct? thanks in advance

 

[wakejosh]

Note the expression: y = A/x2. Which statement is most consistent
with this expression?

a. y is less than x
b. if x is halved, y is multiplied by 4
c. y is greater than x
d. if x is doubled, y is multiplied by a factor of 2
e. y is equal to x


I find that A seems to be true,, but the wording on D confuses me a bit.

 

[drpizza]

OOOOPS, give me a moment... I'm rusty with LaTeX

It's always a good idea to write your units down when you're doing calculations. The technique I teach is "multiply by 1"... that is, if the numerator = the denominator, the value of the fraction is one.
\frac{3 feet}{36 inches}=1 because the numerator equals the denominator.

Now, all you have to do is worry about the units you don't want cancelling out each step of the way.

You could use \frac{88 foosi}{6.90feet} as a multiplier, or you could use \frac{6.90feet}{88 foosi} as a multiplier (to multiply by 1.

Now, you're starting with \frac{94 foosi}{1} If you multiply it like this: \frac{94 foosi}{1}*\frac{88 foosi}{6.90 feet}, then your units work out to foosi squared per foot. Not what you want.

So, you multiply \frac{94 foosi}{1}*\frac{6.90 feet}{88 foosi} And, your units work out to feet.

for what it's worth, "5.9/88" is not "= 14.92". You meant 88/5.9

 

[geoffjb]

On planet Z, the standard unit of length is the foose. Ann the
Astronaut is 5.90 feet tall on
earth. She lands on planet Z and is measure to be 88 foosi
(plural of foose) tall. Her crew
member Rachael is 94 foosi tall. How tall is Rachael in Earth
measurements?

i get 6.3 feet

5.9/88 = 14.92

94/14.92 = 6.3

is this correct? thanks in advance

\frac{5.90 feet}{88 foosi} = \frac{x feet}{94 foosi}

88 foosi\,x = (5.9 feet)(94 foosi)

x = \frac{(5.9 feet)(94 foosi)}{88 foosi}

 

[drpizza]

:) Or you could do it as a proportion as Geoff did... The proportion method is easier for this type of a conversion; my method above works very well if you're converting something like miles per hour to meters per second.

 

[wakejosh]

where did you get 6.9? is that a typo? did you mean 5.9?

anyway, I run the numbers geoff did and I get 6.3 again..so I assum my answer is correct. thanks for the help

 

[geoffjb]

where did you get 6.9? is that a typo? did you mean 5.9?

anyway, I run the numbers geoff did and I get 6.3 again..so I assum my answer is correct. thanks for the help

Yes, your answer's correct.

 

[drpizza]

yes, 6.9 was a typo... or rather, a memory problem. :)

 

[wakejosh]

great thanks.. one other quick question: can I just multiply 3.47 m/s/s by 5 seconds to get my speed after that amount of time? for example:

. A European sports car dealer claims that his car will accelerate
at a constant rate from rest
to a speed of 100 km/hr (28 m/s) in 8.00 s. What is the speed
after the first 5.00 s of
acceleration?

a.44.4 m/s b. 34.7 m/s c. 28.7 m/s d. 17.4 m/s e. 8.7
m/s


First I find the acceleration to be 3.47 m/s^2 now can i just times by 5? If so i get 17.4 m/s Is this correct?