# Suppose y is inversely proportional to x. If y = 6 when x = 4, how do you find the constant of proportionality and write the formula for y as a function of x and use your formula to find x when y = 8?

##### 2 Answers

If

then

Using this formula we find that if

#### Explanation:

Given,

or

this is if and only if

Also, we know that if

then

this gives us our formula

Then consider when

then

# K = 24 #

# y = 24/x#

# x = 3 # when# y = 8 #

#### Explanation:

"y is inversely proportional to x":

# => y prop 1/x #

# :. y = K 1/x = K/x#

"If

# => 6 = K/4 #

# :. K = 24 #

"write the formula for y as a function of x"

# K = 24 => y = 24/x#

"use your formula to find

# y = 8 => 8 = 24/x #

# :. x=24/8 = 3 #