&&66 AF 1.4*0' Use and$SSO\WKHDUHDDQGSHULPHWHUIRUPXODVIRUUHFWDQJOHVLQUHDOZRUOG interpret formulas (e.g., area ! length # width or DQGPDWKHPDWLFDOSUREOHPV)RUH[DPSOHILQGWKHZLGWKRIDUHFWDQJXODUURRPJLYHQWKH A ! lw) to answer questions about quantities and their DUHDRIWKHIORRULQJDQGWKHOHQJWKE\YLHZLQJWKHDUHDIRUPXODDVDPXOWLSOLFDWLRQ relationships. HTXDWLRQZLWKDQXQNQRZQIDFWRU
basic facts; meaning of variable; multiplication
Use Formulas for Perimeter Perimeter is the distance around a figure. You can find perimeter by adding the lengths of all the sides.
a
K
ey Ide
s
l w
w
s
s s
l
P!l"l"w"w P!s"s"s"s You can also use these formulas to find the perimeters of rectangles and squares. Rectangle: Square: P ! 2l " 2w P ! 4s
E x am p l E
1
P P P P
! ! ! !
2l " 2w (2 # 6) " (2 # 4) 12 " 8 20 in.
w ! 4 in.
l ! 6 in.
E x am p l E
2
Find the perimeter of a square when s ! 6 feet. P ! 4s P!4#6 P ! 24 feet
Solve each problem. 10. Charles is putting a fence in his back yard for a dog run. He wants the dog run to be 20 ft and 6 ft wide. How many feet of fencing does he need?
11. Carole bought a rug with a perimeter of 36 feet. The rug is 8 feet wide. How long is it?
10 feet
52 feet Math Reasoning
Formulas for Perimeter
MR 2.3
12. Explain how using the formula for finding the perimeter of a square relates to adding the lengths of the sides.
Since there are 4 sides to add that are the same length, you can multiply the length of one side by 4. Chapter 19 – Lesson 2
page 221
MCX94.HW.CL.G4.FM&Lesson.v211
8/2/04
19:16
Page 148
Name
…at home!
P RAC T I C E Find the perimeter of each rectangle and square. 1.
2.
w 3 ft
l 8 ft
l 9 ft w 13 ft
24 feet
42 feet
3. l 18 in.
4. l 23 ft
w 15 in.
w 11 ft
66 in.
68 ft
5. l 2.7 ft
6. s 9.5 ft
w 1.3 ft
Solve each problem. 7. Charles is putting a fence in his back yard for a dog run. He wants the dog run to be 30 ft long and 12 ft wide. How many feet of fencing does he need?
8. Carol bought a rug with a perimeter of 56 feet. The rug is 8 feet wide. How long is it?
20 feet
84 feet Math Reasoning
Formulas for Perimeter
MR 2.3
9. Explain how using the formula for finding the perimeter of a square relates to adding the lengths of the sides.
Since there are 4 sides to add that are the same length, you can multiply the length of one side by 4. page 148
Solve each problem. 10. Charles is putting a fence in his back yard for a dog run. He wants the dog run to be 20 ft and 6 ft wide. How many feet of fencing does he need?
11. Carole bought a rug with a perimeter of 36 feet. The rug is 8 feet wide. How long is it?
10 feet
52 feet Math Reasoning
Formulas for Perimeter
MR 2.3
12. Explain how using the formula for finding the perimeter of a square relates to adding the lengths of the sides.
Since there are 4 sides to add that are the same length, you can multiply the length of one side by 4. Chapter 19 – Lesson 2
Student Book Page
page 221
Name
…at home!
P RAC T I C E Find the perimeter of each rectangle and square. 1.
2.
w 3 ft
l 8 ft
l 9 ft w 13 ft
24 feet
42 feet
3. l 18 in.
4. l 23 ft
w 15 in.
w 11 ft
66 in.
68 ft
5. l 2.7 ft
6. s 9.5 ft
w 1.3 ft
Solve each problem. 7. Charles is putting a fence in his back yard for a dog run. He wants the dog run to be 30 ft long and 12 ft wide. How many feet of fencing does he need?
8. Carol bought a rug with a perimeter of 56 feet. The rug is 8 feet wide. How long is it?
20 feet
84 feet Math Reasoning
Formulas for Perimeter
MR 2.3
9. Explain how using the formula for finding the perimeter of a square relates to adding the lengths of the sides.
Since there are 4 sides to add that are the same length, you can multiply the length of one side by 4. page 148
