Thursday, 5 December 2019

Perimeter and Area (Practice Set 45)

Practice Set 45


Important Formula : 

Area of a square =(side²) 

Area of a rectagle = Length X Breadth


1) Find the area of a square having side 12 cm.
-> Area of a square =(side²) 
                                = ( 12 X 12)
                                = 144 cm²

2) The length of a rectangle is 15cm and breadth is 5 cm. Find its area?
->  The Area of a rectangle = Length X Breadth
                                          = 15 X 5
                                          = 75 cm²

3) The area of a rectangle is 102 cm². If its length is 17 cm. What is its perimeter?
-> (Here, area if rectangle is given as 102 and length as 17 but breadth is not given)
Area of a rectangle = Length X Breadth
∴           102             = 17 X Breadth
∴     102 /17             = Breadth
∴       6    = Breadth
The perimeter of rectangle = 2(l + b)
                                            = 2 (17 + 6)
                                            = 2 X 23
                                            = 46 cm

4) If the side of a square is tripled, how many times will its area be as compared to the area of the original square?
-> Let the side of the square be x cm
∴ Area of square = x X x
∴                          = x²cm
Now, If the side of a square is tripled, then its side will be 3x
∴ Area of new square = 3x X 3x
∴                                 = 9x² cm
∴ 9x² is 9 times of x²
∴ The area of the new square is 9 times the area of the original square.

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