y is directly proportional to x. y=36 when x=5. By writing an equation of proportionality, work out the value of y when x=8.
To find the equation of proportionality, we need to determine the constant of proportionality between y and x.
We know that y is directly proportional to x, and when x=5, y=36. Let's use this information to find the constant of proportionality (k).
The equation of proportionality can be written as: y = kx.
We can substitute the values we know into this equation to solve for k:
36 = k * 5
To isolate k, divide both sides of the equation by 5:
k = 36 / 5 = 7.2
Therefore, the equation of proportionality is: y = 7.2x.
To find the value of y when x=8, substitute x=8 into the equation:
y = 7.2 * 8
y = 57.6
Therefore, when x=8, y is equal to 57.6.
To find the value of y when x=8, we can use the concept of direct proportionality. Direct proportionality means that y increases or decreases in direct proportion to x.
We are given that y is directly proportional to x and that y=36 when x=5. To write the equation of proportionality, we need to find the constant of proportionality, denoted as k.
To find k, we can use the given values of y and x:
k = y / x
k = 36 / 5
k = 7.2
Now that we have the value of k, we can write the equation of proportionality:
y = kx
Substituting the value of k, we have:
y = 7.2x
To find the value of y when x=8, we substitute x=8 into the equation and calculate:
y = 7.2 * 8
y = 57.6
Therefore, when x=8, y=57.6.
y = kx
so, y/x = k, a constant
so, you want
y/8 = 36/5