There are 180 in half a circle because 1/2=180,2/1=180,100/100=180, and 80/80=180 and those are all part of half a circle. Another reason why it’s 180 because there is 200 parts in a circle, so you need to subtract 200-180=180 (please check my calculation with a calculator if it’s not the right answer then it’s something that subtracts has to do with the number 200 so 200 would be in the subtraction and the equation has to equal 180). Hope this helps :)
