# Question #f7758

##### 2 Answers

We can know if something is a direct variation, if both the quantities increase or decrease simultaneously.

#### Explanation:

Direct variation means: When the value of

Writing with proportionality sign:

When the proportionality sign is replaced by equal- to sign, a proportionality constant is to be multiplied:

Given : y=5 when x=160,

OR

We will first calculate the value of proportionality constant from above equation:

Asked :what is

We can see that as the value of

Hence we can know if something is a direct variation by observing the variation proportionality.

When the value of one variable decreases with increase in value of other (and vice versa), it is inverse variation. Ex: If the speed of a vehicle is more, the time taken to cover a certain distance is less. Here Speed and time are the variables which are inversely proportional.

#### Explanation:

#"the initial statement is "ypropx#

#"to convert to an equation multiply by k the constant"#

#"of variation"#

#rArry=kx#

#"to find k use the given condition"#

#y=5" when "x=160#

#y=kxrArrk=y/x=5/160=1/32#

#"equation is " color(red)(bar(ul(|color(white)(2/2)color(black)(y=x/32)color(white)(2/2)|)))#

#"when "x=368#

#y=368/32=11.5#