# inverse proportionality

• Jan 26th 2010, 07:47 AM
andyboy179
inverse proportionality
This is my question:
While doing underwater tests in one part of an ocean, a team of scientists noticed that the temperature in degrees celsius was inversely proportional to the depth in kilometres. When the temperature was 6 degrees celsius, the scientists were at a depth of 4km.

i worked out that K= 24

A) To what depth would they have had to go to find the temperature at 2 degrees celsius?

would i do this for the answer:
24/2= 12?

thanks for any help in advance!
• Jan 26th 2010, 08:20 AM
Manx
right!
Good job. Can you do a similar problem with numbers that are not so friendly?
• Jan 26th 2010, 08:22 AM
andyboy179
Quote:

Originally Posted by Manx
Good job. Can you do a similar problem with numbers that are not so friendly?

umm im not sure
• Jan 26th 2010, 08:32 AM
Manx
If y and x are inversely proportional, they are related by the equation, y=k/x. (Ther 'inverse' part puts x in the denominator. For direct proportions or 'varyies directly', x would be in the numerator with k.)
Use the given situation to find k. (24 in this problem)
Then in this situation, y=24/x for whatever values of x or y anyone wants to throw at you.
If the 'given' numbers had not been so friendly, we could have still used the same process. Sometimes our brains kind of figure out the answer without telling us how they did it! That's when it's important to know mathematics, so we can slow things down to an understandable pace!
• Jan 26th 2010, 08:33 AM
Manx
Sorry about the typos in the previous reply. I should have proofread it BEFORE I sent it!!!
• Jan 26th 2010, 08:34 AM
andyboy179
Quote:

Originally Posted by Manx
If y and x are inversely proportional, they are related by the equation, y=k/x. (Ther 'inverse' part puts x in the denominator. For direct proportions or 'varyies directly', x would be in the numerator with k.)
Use the given situation to find k. (24 in this problem)
Then in this situation, y=24/x for whatever values of x or y anyone wants to throw at you.
If the 'given' numbers had not been so friendly, we could have still used the same process. Sometimes our brains kind of figure out the answer without telling us how they did it! That's when it's important to know mathematics, so we can slow things down to an understandable pace!

i don't know how to do that yet, he haven't been told how to. can you help me on another question that im not sure on?
• Jan 26th 2010, 08:37 AM
Manx
I'll try.
• Jan 26th 2010, 08:48 AM
andyboy179
thanks!

A new engine was being tested, but it had serious problems. the distance it went, in km, without breaking down was inversely proportional to the square of its speed in m/s. When the speed was 12m/s, the engine lasted 3km.
3 x 144=432
K=432?
• Jan 26th 2010, 09:03 AM
Manx
woohoo!
You go Andyboy!
• Jan 26th 2010, 09:35 AM
andyboy179
Quote:

Originally Posted by Manx
You go Andyboy!

so it was correct?
• Jan 26th 2010, 09:48 AM
Manx
YES!