Chapter 3 Lesson 7 Using Formulas pgs What you will learn: Solve problems by using formulas Solve problems involving the perimeters & areas of rectangles What you will learn: Solve problems by using formulas Solve problems involving the perimeters & areas of rectangles

Vocabulary: Formula (131): an equation that shows a Relationship among certain quantities. A formula Usually contains two or more variables. Perimeter (132): the distance around a geometric figure Area (132): the space inside a geometric figure expressed as square units Formula (131): an equation that shows a Relationship among certain quantities. A formula Usually contains two or more variables. Perimeter (132): the distance around a geometric figure Area (132): the space inside a geometric figure expressed as square units

Key Concept (131) Distance Formula Words: Distance equals the rate multiplied by the time Variables: Let d= distance, r = rate, & t = time Equation: d = rt Words: Distance equals the rate multiplied by the time Variables: Let d= distance, r = rate, & t = time Equation: d = rt What is the rate in miles per hour of a dolphin that travels 120 miles in 4 hours? d = rt 120 = r4 Make it look pretty! 4r = 120 4r = r = 30 The dolphin travels at a rate of 30 mph

Key Concept (132): Perimeter of a Rectangle Words: The perimeter of a rectangle is twice the sum of the length and width Symbols: P = l + l + w + w Use the way you or P = 2 l + 2 w prefer! or P = 2 (l + w) l Model: w Perimeter of a Rectangle Words: The perimeter of a rectangle is twice the sum of the length and width Symbols: P = l + l + w + w Use the way you or P = 2 l + 2 w prefer! or P = 2 (l + w) l Model: w

Key Concept (132): Area of a Rectangle Words: The area of a rectangle is the product of the length and width Symbols: A = lw l Remember area is Model: w expressed in square units Area of a Rectangle Words: The area of a rectangle is the product of the length and width Symbols: A = lw l Remember area is Model: w expressed in square units

Apply what you know! Find the perimeter of a rectangle. 8 ft. 4 ft The perimeter of this rectangle is 28 meters. Its width is 8 meters. Find the length. P = 2( l + w) P = 2(8+4) P = 2(12) P = 24 ft. P = 2( l+w) 28 = 2( l+ 8) 28 = 2 l = 2 l = 2 l = l 8m Check: 24 = 2(8+4) 24 = 2(12) 24 = 24  28 = 2(6+8) 28 = 2(14) 28 = 28 

Apply more of what you know! Find the area of the rectangle: 12 in. 10 in. A = lw A = 12(10) A = 120 in 2 The area of a rectangle is 323 square yards. Its length is 17 yards. Find the width. A = lw 323 = 17 w 323 = 17 w w = 19 yds Check: A = lw 323 = 17(19) 323 = 323  Check: 120= 12(10) 120 = 120 

Find the perimeter and area of each rectangle: 6 mi 4 mi 18 in. 50 in. A= lw A = 6(4) A = 24 mi 2 P = 2( l+w) P = 2(6 + 4) P = 2(10) P = 20 mi Check: 20= 2(6+4) 20= 2(10) 20 = 20  P = 2( l+w) P = 2( ) P = 2(68) P = 136 in. Check: 136 = 2(18+50) 136 = 2(68) 136 = 136  A= lw A = 18(50) A = 900 in 2

Find the missing dimension: 7m w P = 24m A = 176 yd 2 w 16yd P = 2 (l+w) 24 = 2(7+ w ) 24 = w = w 10 = 2 w 2 2 w = 5m Check: 24=2(7+5) 24=2(12) 24=24  A = lw 176 = 16 w w = 11yd Check: 176=16(11) 176=176 

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