Suppose that y is directly proportional to x.
If y = 10 when x = −5, what is the value of y when x = 30?
"y is directly proportional to x" --- y = kx , where k is a constant
for the given:
10 = -5k
k = -2
so y = -2x is your equation:
so when x = 20 , y = ......
sym
If y is directly proportional to x, it means that y = kx, where k is the constant of proportionality. We can find the value of k by using the given information.
We know that y = 10 when x = -5. Plugging these values into the equation, we get:
10 = k(-5)
To find the value of k, we can solve for it:
k = 10 / (-5)
k = -2
Now that we have the value of k, we can use it to find the value of y when x = 30. Plugging these values into the equation, we get:
y = (-2)(30)
y = -60
Therefore, when x = 30, y = -60.
To find the value of y when x = 30, we can use the concept of direct proportionality.
When two variables are directly proportional, it means that their ratio remains constant. In this case, we can write the proportion as:
y/x = k
Where k is the constant of proportionality.
To find the value of k, we can substitute the given values in the proportion:
10 / (-5) = k
Now, let's solve for k:
k = -2
Now that we have the value of k, we can use it to find the value of y when x = 30:
y / 30 = -2
To solve for y, we can cross-multiply:
y = -2 * 30
y = -60
Therefore, when x = 30, the value of y is -60.