Explanation:
4a.
the circumference of a circle is
2×pi×r
we know, r = 6 cm.
so the whole circumference is
2×pi×6 = 12×pi = 37.69911184... cm
4b.
the arc BC is the part of the full circumference that corresponds to 120° out of the 360° of a full circle.
the arc BC is then
12×pi × 120/360 = 12×p × 1/3 = 4×pi = 12.56637061... cm
the perimeter of the shaded area (pie slice) is the arc BC plus 2 radius lengths (from the arc points to the center of the circle)
12.56637061... + 2×6 = 12.56637061... + 12 =
= 24.56637061... cm
4c.
the area of a circle is
pi×r²
in our case
pi×6² = 36pi = 113.0973355... cm²
the area of the shaded area (pie slice) is the 120° part of the full 360° circle area :
36pi × 120/360 = 36pi × 1/3 = 12pi = 37.69911184... cm²