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This Lesson (BASIC FORMULAE FOR FINDING AREA AND PERIMETER OF A RECTANGLE.) was created by by Timnewman(323)
  About Timnewman: Tim is from the department of mathematics Kogi State college of education Ankpa. Kogi State,Nigeria. Feel free to email me at timtimazubuike@gmail.com for the solution of your mathematics problem or explanation of any concept in maths.it is absolutel
The basic formulae for Finding the area and perimeter of a rectangle is designed to help you know the appropriate formula to use when dealing with area and perimeter of a rectangle. AREA OF A RECTANGLE An area (A) of a rectangle is a space covered by that rectangle.The area is given by; A=L*W where A=area,L=length of the rectangle,W=width of the rectangle. EXAMPLE 1: Find the area of a rectangle given that its length of width is 4cm and 2cm respectively. Solution. A=L*W but L=4cm,W=2cm Therefore, A=4cm*2cm A=8cm^2 The area of the rectangle is 8cm*2 EXAMPLE 2: Find the length of a rectangle given that its area is 8cm^2 and its width is 2cm. SOLUTION A=L*W from the question,A=8cm^2 and W=2cm Then, 8=L*2 8=2L divide both side by 2 8/2 = 2L/2 4=L i.e, L=4cm. The length of the rectangle is 4cm. PERIMETER OF A RECTANGLE. Perimeter (P) of a rectangle is the sum of the four sides of the rectangle. Note:rectangle has four sides of which two opposite sides are equal.(i.e two length equal and two width equal.) Now if we add these sides,we have that perimeter (P)=L+L+W+W P=2L+2W P=2(L+W)------This is the formula for perimeter of a rectangle. EXAMPLE 3: A rectangle has a length of 4cm and width of 2cm.find its perimeter. SOLUTION Using perimeter formula, P=2(L+w) But L=4cm,w=2cm Then, P=2(4cm+2cm) P=2(6cm) P=12cm. The perimeter of the rectangle is 12cm. Note:The unit of area is squared unit but that of perimeter is not. AREA AND PERIMETER RELATIONSHIP. Sometimes,you may be given area and perimeter of a rectangle which you may be required to find its length and width.To tackle this type of problem,study example 4 below. EXAMPLE 4: The area of a rectangle is 6cm^2 and its perimeter is 10cm.find the length and width of the rectangle. SOLUTION From the above, Area (A) is 6cm^2 i.e. LW=6------(1) also, perimeter (P)=10cm ie 2(L+W)=10-----(2) divide both side of equation 2 by 2 L+W=5------(3) from equation 3,, L=5-W------(4) put (4) in (1) (5-W)W=6 5W-W^2-6=0 W^2-5W+6=0 factories the quadratic equation (W-2)(W-3)=0 Therefore, W=2cm or W=3cm When W=2cm from (4) L=5-2 L=3cm Hence,the length and width of the rectangle is 3cm and 2cm respectively. This lesson has been accessed 2174 times. |
