x varies inversely as y2, and x = 4 when y = 10. Find x when y = 2.

A. x = 16
B. x = 5
C. x = 80
D. x = 100

Question

x varies inversely as y2, and x = 4 when y = 10. Find x when y = 2.

A. x = 16	
B. x = 5	
C. x = 80	
D. x = 100

anonymous · Answer

doryy cant give you just the answer

anonymous · Answer

Can you help me work it out then?

amistre64 · Answer

yes

amistre64 · Answer

do you recall the 2 basic forms that this type of question takes?

anonymous · Answer

No.

amistre64 · Answer

the is the direct variation:  y = kx
and the indirect variation:  y = k/x

which one of these do you spose this question would need to use

anonymous · Answer

I don't know, honestly... I haven't paid attention to math since 7th grade and now I'm in  12th and I greatly regret it.

amistre64 · Answer

just humor me and take a guess, its a 50/50 shot

anonymous · Answer

y = k/x

amistre64 · Answer

lol, very good :)

amistre64 · Answer

so, lets use this form as it pertains to the question

amistre64 · Answer

"x varies inversely as y^2" tells us:

y^2 = k/x

"x = 4 when y = 10" are the specifics

10^2 = k/4

cam you solve for k?  we need it for the next step

anonymous · Answer

uh 20?

amistre64 · Answer

... not even close, but nice try ;)

anonymous · Answer

Haha

amistre64 · Answer

10^2 = k/4

100 = k/4

4(100) = k

400 = k

anonymous · Answer

oh okay

amistre64 · Answer

now, lets delete the x,y values and keep the k

y^2 = 100/x ; and it asks us to find x when y = 2, so lets plug it in

2^2 = 100/x

how would you suggest we solve for "x"?

anonymous · Answer

uhhh i have no idea >.< I probably seem like a dumbass. :\

amistre64 · Answer

and k=400, not 100 ... but thats just these fat little fingers trying to type :)

amistre64 · Answer

these are basic algebra techniques that you will certainly have to practice more ....

2^2 = 400/x

4 = 400/x

4x = 400

x = 400/4

now what would you say x is equal to?

anonymous · Answer

100

amistre64 · Answer

yay!!, i agree  ;)

anonymous · Answer

so that's the answer then right?

amistre64 · Answer

i hope so, or else im gonna have to go back to 3rd grade ....

anonymous · Answer

>.< alright haha thanks

amistre64 · Answer

good luck :)

anonymous · Answer

How would I do this one? http://prntscr.com/kvs6b

amistre64 · Answer

that one would take a lot of work that you presently do not have the background to solve ...

post it as a new question, and let someone else have the chance to get a medal by guiding you thru it

anonymous · Answer

alright. :)