(b) 18 cm
Solution:
(Answer may vary)
NCERT Textbook Page 143
Preetha and Adrit’s grandmother is making a rug with square patches. The picture below shows the rug. How many patches have they used to make this?
Solution:
They have used 90 square patches to make the rug.
Preetha and Adrit are trying to cover their table with different shapes. Preetha covered it with triangles and circles. Adrit covered with squares and rectangles.
They found that __________, __________ and __________ shapes cover the top of the table without gaps and overlaps. __________ shape leaves gaps.
__________ triangles cover Table 1.
__________ squares cover Table 3.
__________ rectangles cover Table 4
Solution:
They found that triangle, square and rectangle shapes cover the top of the table without gaps and overlaps. Circle shape leaves gaps.
20 triangles cover Table 1.
8 squares cover Table 3.
12 rectangles cover Table 4.
Do circles tile? Can we use them to cover a region?
The area of Table 1 is __________ triangle units.
The area of Table 3 is __________ square units.
The area of Table 4 is __________ rectangle units
Solution:
No, circles do not tile. We cannot use them to cover a region because circles leave gaps.
The area of Table 1 is 20 triangle units.
The area of Table 3 is 8 square units.
The area of Table 4 is 12 rectangle units.
Now, try to cover the top of your table without gaps and overlaps with the following objects of same size.
(a) Notebooks
(b) Lunch boxes
(c) Pencil boxes
(d) Maths textbooks
Which of the above objects covered the region completely?
Solution:
Do it yourself.
NCERT Textbook Page 144
Let Us Do
Preetha is playing with tiles. She covers her desk with different shapes as shown below.
Look at the different tiles on her desk and answer how many of the following shapes will cover the desk.
(a) Green triangles
(b) Red triangles
(c) Blue squares
Solution:
In the given picture, we can see that the desk is made of 54 squares.
(а) 2 green triangles = 1 square
2 × 54 = 108 green triangles = 54 squares
Therefore, 108 green triangles will cover the desk.
(b) 1 red triangle = 4\(\frac{1}{2}\) squares = \(\frac{9}{2}\) squares
Since there are 54 squares on the desk. Therefore, required number of red triangles = 54 ÷ \(\frac{9}{2}\)
\(\frac{54 \times 2}{9}\) = 12
Therefore, 12 red triangles will cover the desk.
(c) 1 blue square = 1 square
Therefore, 54 blue squares will cover the desk.
NCERT Textbook Pages 145-147
Let Us Do