1. A rectangular board is 50 cm long and 60 cm
wide. A border of 6 cm width is running all
along the edges. Find the area of the border.
Answers
Step-by-step explanation:
Mathematics NCERT Grade 7, Chapter 11: Perimeter and Area- This chapter gives all the details about the perimeter and area of plane figures. Firstly the chapter discusses squares and rectangles.
Perimeter is the distance around a closed figure whereas area is the part of the plane occupied by the closed figure.
The perimeter of the following geometrical shapes are discussed in the first section:
Square
Perimeter of a square = 4 × side
Rectangle
Perimeter of a rectangle = 2 × (length + breadth)
The section is divided into two sub-parts:
1. Triangles as parts of rectangles
2. Generalising for other congruent parts of rectangles
Before moving onto exercise 11.2, the topics Area of triangle and parallelogram are discussed.
Area of a square = side × side
Area of a rectangle = length × breadth
Area of a parallelogram = base × height
Area of a triangle =1/2 × base × height
In the other half of the chapter, circles are explained. The topic is explained in two parts:
1. Circumference of Circle
The distance around a circular region is known as its circumference.
Circumference of a circle = ππd
2. Area of circle
Area of circle is given by ππr2
The last part of the chapter is about the conversion of units and application of the formulas.
Based on the conversion of units for lengths, studied in the chapter, the units of areas can also be converted:
1 cm2 = 100 mm2
1 m2 = 10000 cm2
1 hectare = 10000 m2
The various formulas and the conversions of units are revised and thus their application in real life scenarios are studied in this topic. These questions require practice and thus one needs to try and solve as many questions as possible in this chapter.
Students will be briefed about important points of the chapter perimeter and area in the end.