Question

M is directly proportional to r2.when r=2,m=14.Work out the value of r when m =224

Answer 1

Answer:

$r=8$

Step-by-step explanation:

we know that

A relationship between two variables, x, and y, represent a proportional variation if it can be expressed in the form  $y=kx$

In this problem

Let

$y=m$

$x=r^{2}$

substitute

$m=kr^{2}$

Find the value of k

For $r=2, m=14$

$14=k(2^{2})$

$14=4k$

$k=14/4$ ----> constant of proportionality

the equation is equal to

$m=(14/4)r^{2}$

Find the value of r when m=224

substitute in the equation and solve for r

$224=(14/4)r^{2}$

$r^{2}=224*4/14$

$r^{2}=64$

$r=8$