Samacheer Kalvi Class 4 Maths Solutions Term 1 Chapter 1 Geometry InText Question

Activity (Text Book Page No. 8)

Question 1. Measure the radius and diameter of the following circles.
Answer:The measurements for the circles are:
1. Radius = 1 cm, Diameter = 2 cm
2. Radius = 1.7 cm, Diameter = 3.4 cm
3. Radius = 0.7 cm, Diameter = 1.4 cm Each diameter is exactly double its corresponding radius.
In simple words: The radius is the distance from the center to the edge of a circle. The diameter is the distance straight across the circle, passing through the center. The diameter is always two times the radius.

🎯 Exam Tip: Remember that diameter = 2 × radius. Use a ruler to measure accurately from the center to the edge for the radius, and across the center for the diameter.

 

Activity (Text Book Page No. 9)

Question 2. Measure the sides and identify the names of different objects and find the differences among them and fill the table given below. The objects are: (a) Chessboard, (b) Postcard, (c) Window, (d) Paper, (e) Newspaper, (f) Maths Kit box, (g) Kite.

Answer:This table shows how different shapes like squares, rectangles, parallelograms, and rhombuses are defined by their sides, corners (vertices), and how their diagonal lines behave. For example, a square has all sides equal and its diagonals are the same length.
In simple words: Different shapes have different numbers of equal sides and corners. Also, the lines that cross them (diagonals) can be equal or unequal.

🎯 Exam Tip: To compare shapes, focus on key features like side lengths (all equal, opposite equal) and diagonal properties (equal, bisecting). Practicing with real-world objects helps in understanding these geometric properties.

 

Activity (Text Book Page No. 12)

Question 3. Arrange the tangram pieces to from pictures.
The question shows two sets of tangram pieces and asks you to arrange them to form pictures.
Answer:1. The tangram pieces can be arranged to form a picture of a bird.
2. The tangram pieces can be arranged to form a picture of a house. Tangrams are a fun way to learn about shapes and how they fit together to create new forms.
In simple words: You need to move and turn the tangram shapes to make the given pictures.

🎯 Exam Tip: When arranging tangram pieces, look for matching edges and angles. Try to visualize how the smaller shapes fit into the larger outline of the final picture.

 

Activity (Text Book Page No. 14)

Question 4. Which tile will you choose to fill the space given below and find how many tiles are needed to fill the given space. The space is a rectangle of 10 cm height and 15 cm width. Two types of tiles are shown: (a) a tile with sides 2cm and 3cm, (c) a tile with sides 2cm and 5cm.
Answer:The tile chosen is (a), which has sides 2 cm and 3 cm. To calculate the number of tiles, we find the perimeter of the tile.
Perimeter of tile = 2 cm + 3 cm + 2 cm + 3 cm = 10 cm.
Number of tiles needed = 5. This means five tiles of 2 cm by 3 cm can fit along one edge of the larger space, effectively filling it.
In simple words: We pick the tile that is 2 cm by 3 cm. If we place these tiles side by side along one edge, we need 5 of them to cover the space.

🎯 Exam Tip: When filling a space with tiles, consider both the area and how the tiles fit along the edges. Sometimes finding how many tiles fit along one dimension helps quickly determine the total.

 

Activity (Text Book Page No. 14 & 15)

Question 5. Fill the table given below by fixing the appropriate tile in the space given below. The space is a rectangle of 36 cm width and 15 cm height.

Answer:The table shows how many tiles of each shape are needed to perfectly fill the given rectangular space of 36 cm by 15 cm. We can see that most rectangular and square tiles can fit exactly, but the first triangular tile cannot.
In simple words: This table tells us which tile shapes and how many of them can neatly fit into a big rectangular space without any gaps or overlaps.

🎯 Exam Tip: To determine if a tile fits exactly, check if its dimensions are factors of the space's dimensions. For area-based fitting, divide the total area by the tile's area, but also consider how they align along the edges.

 

Activity (Text Book Page No. 16)

Question 6. a. Form the cube by folding the nets given below.
(i) The first net for a cube is shown below.
Answer:When folded, this net forms a cube. A cube is a 3D shape with six identical square faces.
In simple words: If you cut out this flat shape and fold it up, you will make a solid box with all sides equal, called a cube.

🎯 Exam Tip: Imagine folding each flap to see if they meet to form a closed 3D shape. All squares in a cube net must align to form faces without overlap or gaps.

 

Question 7. (ii) The second net for a cube is shown below.
Answer:This net also forms a cube when folded. There are many different ways to unfold a cube into a flat net.
In simple words: This flat pattern, when folded, also creates a cube, showing that a cube can be unfolded in various ways.

🎯 Exam Tip: To confirm a net forms a cube, ensure it has six squares and that opposite faces are correctly placed in the unfolded pattern.

 

Question 8. (iii) The third net for a cube is shown below.
Answer:This final net also successfully folds into a cube. Recognizing different nets for the same shape helps understand 3D geometry.
In simple words: This pattern, when folded, also becomes a perfect cube.

🎯 Exam Tip: Practice identifying all 11 possible nets of a cube to easily recognize if a given pattern can form one.

 

Question 9. b. Use these nets to form cuboids.
(i) The first net for a cuboid is shown below.
Answer:When folded, this net forms a cuboid. A cuboid has six rectangular faces, and opposite faces are identical.
In simple words: This flat pattern, when folded, creates a cuboid, which is like a rectangular box.

🎯 Exam Tip: For a cuboid net, ensure that each pair of opposite faces has the same dimensions. This is key to forming a closed cuboid.

 

Question 10. (ii) The second net for a cuboid is shown below.
Answer:This net also forms a cuboid when folded. Just like a cube, a cuboid can have different net patterns.
In simple words: This different flat shape can also be folded to make a cuboid.

🎯 Exam Tip: Cuboid nets are usually made of rectangles. Check that the arrangement of these rectangles allows them to fold up without leaving any gaps or having overlaps.

 

Question 11. c. Make a cone with semicircle.
Answer:When a semicircle is rotated or folded, its curved edge forms the circular base of the cone, and the straight edges meet to form the slant height. This process creates a three-dimensional cone.
In simple words: If you take a half-circle and fold it, you can make a cone shape. The curved part becomes the bottom circle, and the straight sides join up.

🎯 Exam Tip: Remember that the radius of the semicircle becomes the slant height of the cone, and its arc length becomes the circumference of the cone's base.

 

Question 12. d. Make a cylinder using rectangle sheet.
Answer:When a rectangular sheet is rolled, its length forms the circumference of the cylinder's circular base, and its width becomes the height of the cylinder. Two circular bases are then added to the top and bottom to complete the shape.
In simple words: You can roll up a rectangular piece of paper to make the curved side of a cylinder. Then, you add two circles to the top and bottom to finish the shape.

🎯 Exam Tip: The length of the rectangle forms the circumference of the cylinder's base, while the width of the rectangle forms the cylinder's height.

 

Find Out 2D And 3D Objects From The Given Pictures. (Text Book Page No. 18)

Question 13. Identify whether each object in the pictures is a 2D or 3D shape.
Answer:Here is the classification of each object:
1. Chessboard: 2D
2. Green Cube: 3D
3. Framed Picture (Fox): 2D
4. Pergola (structure): 3D
5. Rubik's Cube: 3D
6. Salt Shaker (Cylinder): 3D
7. Cake Slice: 2D (the flat face of the slice)
8. Brick: 3D
9. Plate of Food: 2D
10. Currency Notes: 3D (as physical objects with thickness)
11. Book: 3D
12. Peach: 3D
13. Clipboard: 2D
14. Gas Cylinder: 3D
15. Cardboard Box: 3D
16. CD: 2D
17. Computer Monitor: 2D (the screen part)
18. Globe: 3D
2D shapes are flat, like a drawing, while 3D shapes have depth, like objects you can hold.
In simple words: We look at each item to see if it's flat (2D) like a picture or if it's solid and takes up space (3D) like a box.

🎯 Exam Tip: Remember that 2D objects have only length and width, while 3D objects have length, width, and height (or depth). Think about whether you can hold it in your hand or if it's just a flat image.