Question

the quantities x and y are proportional.

x	y
7	77
9	99

find the constant of proportionality (r) in the equation y = r x.

r = \boxed{}

Explanation:

Step1: Rearrange for r

From $y = rx$, solve for $r$:
$r = \frac{y}{x}$

Step2: Substitute first pair

Use $x=2, y=22$:
$r = \frac{22}{2} = 11$

Step3: Verify with second pair

Use $x=7, y=77$:
$r = \frac{77}{7} = 11$

Step4: Verify with third pair

Use $x=9, y=99$:
$r = \frac{99}{9} = 11$

Answer:

11