Question

1. What is the circumference of the circle whose radius is :
(i) 7.7 cm?
(ii) 4.9 cm? (iii) 2.1 cm?
(iv) 8.4 cm?
please give step by step answer​

Answer 1

Answer:

I) 48.4 cm, 2) 30.8 cm, 3)13.2 cm&4) 52.8 cm

Step-by-step explanation:

1) circumference of circle = 2πr

=2×22/7×7.7

=2×22×1.1

=48.4

solve other problems in this way

Answer 2

Step-by-step explanation:

Given:

• Measure of three radii of circle.

To Find:

• What is the circumference of the circle with each radii ?

Solution: As we know that circumference of circle is given by 2πr.

Let's find out the circumference with different radii of circle.

• Taking π = 22/7

(i) 7.7 cm

➟ 2 × 22/7 × 7.7

➟ 44/7 × 7.7

➟ 44 × 1.1

➟ 48.4 cm

(ii) 4.9 cm

➟ 2 × 22/7 × 4.9

➟ 44/7 × 4.9

➟ 44 × 0.7

➟ 30.8 cm

(iii) 2.1 cm

➟ 2 × 22/7 × 2.1

➟ 44/7 × 2.1

➟ 44 × 0.3

➟ 13.2 cm

(iii) 8.4 cm

➟ 2 × 22/7 × 8.4

➟ 44/7 × 8.4

➟ 44 × 1.2

➟ 52.8 cm

• A circle is a collection of all points in a plane which are at a constant distance from a fixed point.

• That constant distance is known as Radius and that fixed point is known as Centre of the circle.

• Area of circle = πr²

• For a semi circle of radius r , Perimeter is given by (πr + 2r) and Area is given by 1/2πr².

• Area of ring = π (R² – r²)