Question

If y varies directly with x, and y = 5 when x = 8, how do you write the direct linear variation equation and what is the value of x when y = 15?

Answer 1

look for key words like,varies directly with,varies inversely with,partly constant and partly varies directly or inversely to a certain variable given

Explanation:

first derive a formula from that expression

y=kx

in this case k its a constant so we will find a constant first inorder to derive a formular

substitute the variables with numbers been given

5=k(8) then make k subject of the formular

k=`5/8` then make a formular from the constant

y= `5/8`x

now this is your direct linear equation y= `5/8`x

then use that equetion inorder to find the x value

finding x value, substitute the formula with the value given in this case y=15

then

y= `5/8`x

15= 0.625x

`15/0.625`=x

24=x

therefore x =24