Concentric Circles

Q.

Circles that have the same centre but different radii are called as ____.

1. Co-interior circles

2. Concentric circles

3. Overlapping circles

4. Intersecting circles

Q.

The radii of two circles are $8cm$ and $6cm,$ respectively$.$ Find the radius of the circle having area equal to the sum of the areas of the two circles.

Q.

A circle is a $............$figure, whereas a sphere is a $............$figure.

Q.

If the sum of the areas of two circles with radii $R_1$ and $R_2$ is equal to the area of a circle of radius $R$, then

1. $R_1+R_2=R$

2. $R_1^2+R_2^2=R^2$

3. $R_1+R_2<R$

4. $R_1^2+R_2^2<R^2$

Q.

In an archery board, the radius of the yellow circle is 5cm, and each of the next circle is 2cm more in radius than its previous one. Find the diameter of the black circle.

1. 18cm

2. 22cm

3. 49cm

4. 9cm

Q.

The radii of two circles are 9 cm and 12 cm. The circumference of a circle whose area is equal to sum of the areas of the two circles is:

1. $15cm$

2. $15\pi cm$

3. $30\pi cm$

4. $225cm$

Q.

Floor of a room is an example of:

1. a point

2. a line

3. a circle

4. a plane

Q.

Concentric circle have the same ____.

1. Diameter

2. Radius

3. Center

4. Circumference

Q. Two or more circles can be called concentric if they have the same ______ but different ______.

1. radii, center
2. center, radii
3. diameter, center
4. chords, center

Q. When a stone is droped in a river then circles are formed which have same centre.

1. concentric
2. similar
3. overlapping

Q.

7. Fill in the blanks :

(iii) Diameter of a circle is ______ its radius.

Q.

Explain how diameter is affected by an increase in radius.

Q.

In an archery board, the radius of the yellow circle is 5cm, and the radius of each of the next circles is 2 cm more than the previous ones. Find the diameter of the blue circle.

1. 22 cm

2. 18 cm

3. 9 cm

4. 49 cm

Q.

Circles having the same centre but different radii are called as ___ circles.

1. congruent

2. concentric

3. repeated

4. growing