MG2.1 Use formulas routinely for finding the perimeter and area of basic two-dimensional figures, parallelograms, trapezoids, squares, triangles, circles, prisms, and cylinders. Also: MG3.2 LO: I will evaluate circumference & AREA of a circle using pi, 3.14 (3 and a little more ). Pi ( ) is an IRRATIONAL number that is estimated by the RATIONAL numbers 3.14 & Remember! 9.4 Circumference and AREA, p450 Warm Up 1.The hypotenuse of a right triangle measures 5 in., and one leg measures 3 in. How long is the third leg? 2. To the nearest centimeter, what is the height of an equilateral triangle with sides 9 cm long?
radius Diameter Circumference The circumference of a circle is the distance around the circle. C = d OR C = 2 r Circumference Perimeter OR C = 2r D = r+r = 2r = D d 1 st estimate-use “__ & a little more,” then Use 3.14 for . TIP!
Pi () is an ________ number that is often approximated by the rational numbers 3.14 and. Remember! Find the circumference of each circle to the nearest tenth. 1 st estimate, using “3 and a little more,” then Use 3.14 for . A. circle with a radius=4 m C = 2r = ___(4)m C = __ m 25.__ m C. circle with a diameter = 3.3’ C = d =____(3.3) ft. C = 3.14(___) 10._ ft. B. circle with a radius of 8 cm C = 2 = __(8)(3.14) C =(___) cm _____cm
radius Diameter AREA of a CIRCLE ___() is an ______________ number that is often estimated by the ________ numbers ____ and Remember! “Pies aren’t square, they’re round.”
y (–2, 1) 4 (–2, 5) x Find the AREA of each circle to the nearest tenth. 1 st estimate, using “ and a little more,” then Use 3.14 for . A.circle with center (–2, 1) that passes through (–2, 5). A = r 2 = (__ 2 ) A = r 2 = (__ 2 ) B. circle with a radius of 8 cm Pi () is an ______________ number that is often estimated by the ________ numbers ____ and. Remember!
C. circle with a diameter of 3.3 m A r2 A r2 2 = ____= r Remember! ____________is an _____________ number. ____________ are ______________ numbers that are used to represent (irrational) Pi, (). Find the AREA to the nearest 10 th. 1 st estimate-use “3 & a little more,” then Use 3.14 for . The ride’s distance traveled is the circumference of the Ferris wheel times the number of revolutions, or about ______ 15 = _____’ D. A Ferris wheel has a diameter of 56 feet & makes 15 revolutions per ride. How far would someone travel during a ride? Use for . 9.4 RM & SRe p453