Direct Variation and Inverse Variation? (1 Viewer)

[thebigwillie]

How do u do it? Wot formula do u use? I was trying to do the 2003 paper Question 28 a) and i cant do it. I know its direct variation, but how do u go about doing it? Help will be appreciated thanx

 

[lilmzqt]

wats the question??

 

[malkin86]

y = kx

when y is dependant on x and k is the konstant...

generally you substitute in to find k and then use k in another situation.

 

[thebigwillie]

(a) Sandra is on holiday in Mexico and she plans to buy some silver jewellery.
Various silver pendants are on sale. The cost varies directly with the square of the
length of the pendant. A pendant of length 30 mm costs 130Mexican pesos.
How much does a pendant of length 40 mm cost? (Answer correct to the nearest
Mexican peso.)

 

[thebigwillie]

Thanku So Much:d

 

[lilmzqt]

C= cost, l=length.

C=k(l squared)
when C= 130, l=30 you find k
so...

130 = k x 30(squared)
k=130/900
k=0.1444....

so then u substitute.

C=? k=0.144.... and l=40
so
C= 0.144... x 40(squared)

C= 0.144... x 1600
C= 231.111....

to nearest Mexican Peso
C=231

hope that helps

 

[thebigwillie]

sure does, thanx for ur help peoples

 

[lilmzqt]

SORRY!!!!!!! the first 1 i posted was wrong...i hadda fix it. the one posted now is rite!!! sorry!

 

[thebigwillie]

yeah i looked n i saw an answer, then it disapeared n appeared again! lol. Was wondering where it went! But ya posted it again Thanx again, i really appreciate it!

 

[lilmzqt]

lol....thats okies!

 

[ellie_bubs]

Do you use opposite operations?

Hey i was tryin to do dat question too and i was doing it so that you square root the length cos its sqaured so you are doing the opposite operation, is this what you are suposed to do?

 

[lilmzqt]

nope......i just checked in my text book...the way i did it was rite......oh well

 

[thebigwillie]

wots an example of inverse variation?

 

[cro_angel]

i think its something like.. if theres more people working it takes less time to get something done.. or the cost per person in hiring a hall/room compared to how many people are using it..

 

[lilmzqt]

wots an example of inverse variation?

if, for example, the question is the same as the one you asked about before but it varies INVERSLY instead of directly with watever it would be:

C=k / L^2

 

[Misturi]

we just use y = x/k for inverse...

Is this right?

 

[lilmzqt]

k, being the constant, is on the top. the reason i squared the denominator is becoz i was using the previous question as as example to explain it

 

[Slidey]

(a) Sandra is on holiday in Mexico and she plans to buy some silver jewellery.
Various silver pendants are on sale. The cost varies directly with the square of the
length of the pendant. A pendant of length 30 mm costs 130Mexican pesos.
How much does a pendant of length 40 mm cost? (Answer correct to the nearest
Mexican peso.)

c=kl^2
130=k900
k=130/900=13/90
For a 40mm length pendant,
c=kl^2
c=k*40^2
c=(13/90)*1600
c=231 Mexican Mesos, to the nereast Mecian Meso.

 

[glitterfairy]

A quick definition of direct and inverse variation:

DIRECT: We both win/lose. See it a bit like friends sharing lollies. If one goes up, they both do.

INVERSE: One goes up, one goes down. Like a see-saw.

 

[lilmzqt]

(a) Sandra is on holiday in Mexico and she plans to buy some silver jewellery.
Various silver pendants are on sale. The cost varies directly with the square of the
length of the pendant. A pendant of length 30 mm costs 130Mexican pesos.
How much does a pendant of length 40 mm cost? (Answer correct to the nearest
Mexican peso.)

c=kl^2
130=k900
k=130/900=13/90
For a 40mm length pendant,
c=kl^2
c=k*40^2
c=(13/90)*1600
c=231 Mexican Mesos, to the nereast Mecian Meso.

dont u read? lol. that question was answered some time ago.