57 times 71 = 4047 Hope that helps!
Step-by-step explanation:
<u>Formula:</u>

r represents the radius.
The radius is 1/2 of the diameter.
Since 1/2 of 16 is 8, 8 is our radius.
<u>Substitute:</u>

<u>Solve:</u>


Negative since the answer would be -13
I’m pretty sure the answer is 30!