For the first one write 9 divided by 2 gives your your radius an it’s 3.5. the formula is 2 x 3.14 x radius and that gives you 21.98.
the 2nd one is 2 x 3.14 x 9 = 56.52
the 3rd is 2 x 3.14 x 5= 31.4
formula is always 2 x 3.14 (or pie) x radius
to get your radius from your diameter you do your diameter divided by 2
Answer:

13 glue sticks cost $25.22.
Step-by-step explanation:
4 blue sticks cost $7.76, this means that one glue stick costs
$7.76/4 = $1.94.
Let
be the cost of the glue sticks, and
be the number of glue sticks; then

We can use this equation to find the cost of 13 glue sticks; we just put
into our equation and it gives:

So 13 glue sticks cost $25.22.