1.7 Introduction to Perimeter, Circumference, & Area

Objectives/Assignment Find the perimeter and area of common plane figures. Use a general problem-solving plan. Assignment: 2-32 even

Goal 1: Reviewing Perimeter, Circumference, and Area (width) Perimeter P=2l +2w Area A=lw l (length) Rectangle

Square Perimeter P=4s Area A=s2 S (side)

Triangle Perimeter P=a+b+c Area A= ½ bh a c h (height) b (base)

Circle Diameter d=2r Circumference C=2πr Area A=πr2 radius ** Always use the π button on the calculator; even when the directions say to use 3.14.

Example: Find the perimeter & area of the figure. P=2l +2w P=2(5in)+2(3in) P=10in+6in P=16in A=lw A=(5in)(3in) A=15in2 5 in 3 in

Example: Find the perimeter & area of the figure. P=4s P=4(20m) P=80m A=s2 A=(20m)2 A=400m2 20 m

Example: Find the perimeter & area of the figure P=a+b+c P=5ft+7ft+6ft P=18 ft A= ½ bh A= ½ (7ft)(4ft) A= ½ (28ft2) A= 14ft2 5 ft 4 ft 7 ft 6 ft

Example: Find the circumference & area of the circle. C=2πr C=2π(5in) C=10π in C≈31.4 in A=πr2 A=π(5in)2 A=25π in2 A≈78.5 in2 10in

Goal 2: Using a Problem Solving Plan Ask yourself what you need to solve the problem. Write a verbal model or draw a sketch that will help you find what you need to know. Label known and unknown facts on or near your sketch. Use labels and facts to choose related definitions, theorems, formulas, or other results you may need. Reason logically to link the facts, using a proof or other written argument. Write a conclusion that answers the original problem. Check that you reasoning is correct.

Reminders Vocab Tomorrow! Project Information – Don’t be absent! Test Wednesday