SOME IMPORTANT FORMULA

Area and perimeter of Rectangle and Square 

1. Area of rectangle (A) = length(l) × Breath(b), A = l× b

2. Perimeter of a rectangle (P) = 2 × (Length(l) + Breath(b)), P = 2 × (l + b)

3. Area of a square (A) = Length (l) × Length (l), A = l×l

4. Perimeter of a square (P) = 4 × Length (l), P = 4 ×l

question. 10 A field is 70 m long and 40 m broad. In one corner of the field, a pit which is 10 m long, 8 m broad and 5 m deep, has been dug out. The earth taken out of it is evenly spread over the remaining part of the field. Find the rise in the level of the field.

Solution: Area of the field = (70 × 40) m2 = 2800 m2

Area of the pit = (10 × 8) m2 = 80 m2

Area over which the earth is spread over

Volume of the cube = a3 cubic units

= (2800 – 80) m2 = 2720 m2

Volume of the earth dug out = (10 × 8 × 5) m3 400 m3

Rise in level of the field =

= 250/17 = 14.70 cm

question. 11. A square and a rectangular field with measurements as given in the figure have the same perimeter. Which field has a larger area?

6 cm

8 cm

Solution: meter of rectangle = 2 (Length + Breadth)

= 2 (8 m + Breadth)

= 16 m + 2 × Breadth

It is given that the perimeter of the square and the rectangle are the same.

16 m + 2 × Breadth = 24 m