Answer:
12. $65.90, 13. 36.04cm
Step-by-step explanation:
12. the circumference of the circle is 2pi*r. lets say x is the circumference so x = 2*pi*3.8 = 23.876m. multiply x by 2.76 to get 65.898, round to get 65.90
13. the area of a circle is pi*r^2. the area of the pizza is 12*85=1020cm^2. divide by pi to get 324.676 cm^2. then find the square root to get r=18.019 cm. the diameter = 2r so multiply by 2 to get 36.038cm. I'm not sure what the problem wants to round to so you can round it yourself.
note: for these two problems i used the full pi instead of 3.14. using 3.14 will give you a different answer so it just depends. If the problem wants you to use 3.14, simply resolve the problems and use 3.14 instead of pi wherever required.