Answer:
Formula of circumference: pie(use 3.14 or 22/7) x radius (half of diameter or already given radius) x 2
100 + 100 = 200.
Half of 50(diameter) is 25(new radius). 25(radius) x 3.14(pie) x 2(it always will be there when finding circumference) = 157.
200 + 157 is = 357.
357 is your answer.