instances. Check students' word problems. 8.3 Warm Up. For use before Lesson 8.3. 1. about. 2. 50.24 in. 2. about. 2. 154 ft. 3. about. 2. 3.14 cm. 8...
Answers 8.2 Enrichment and Extension 1. about 25.12 in.
2. about 18.84 m
3. about 34.26 ft
4. about 30.26 yd
5. about 55.4 cm
6. about 50.24 mm
5. about 100.48 m 2
6. about 693 ft 2
7. about 2464 ft 2
8. about 28.26 ft 2
circle whose radius is twice as large; The area formula for the smaller circle can be rewritten as
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2
8.3 Start Thinking!
1 r A = π = π r 2 ; this is one fourth of the 4 2 area of the larger circle.
For use before Activity 8.3
Sample answer: 1. You can divide it into several triangles each with a vertex at the center of the circle. 2. You can put it on grid paper and estimate the number of squares that are covered. 3. You can divide it into tall, narrow rectangles. 8.3 Warm Up For use before Activity 8.3
4. 50 cm
2
2
c. The circle’s area is one fourth of the area of the
8.2 Puzzle Time
1. 63 in.2
r 2
b. A = π
9. a. A = π r 2
10. The radius is 2 units; Set the circumference
equal to the area to get 2π r = π r 2 . So π • r • 2 = π • r • r ; the value of r must be 2. 8.3 Enrichment and Extension
2. 14 m2
3. 66 yd 2
5. 22.4 m
2
6. 1 mm
1. 1.5625
2. 2.25
3. 16%
2
4.
1 9
5. a. 3.5%
8.3 Start Thinking!
b.
For use before Lesson 8.3
22 if the radius 7 is a multiple of 7. It is easier to use 3.14 in all other instances. Check students’ word problems.
Sample answer: It is easier to use
8.3 Warm Up For use before Lesson 8.3
1. about 50.24 in.2
13,816 mi 2
2. about 154 ft 2
c.
3. about 3.14 cm2
8.3 Practice A 1. about 78.5 m 2
2. about 7850 mm 2
3. about 1256 in.2
4. about 38.5 ft 2
5. about 1386 mm 2
6. about 3850 cm 2
7. about 50.24 ft 2
8. about 15,400 cm 2 2
9. about 113.04 in. 11.
99 in.2 224
2
10. about 28.26 in.
12. about 153.86 in.2
8.3 Practice B 1. about 962.5 in.2
2. about 19.625 m 2
3. about 7234.56 mm2
4. about 157 in.2
A42 Big Ideas Math Red Answers
56,834 mi 2
8.3 Puzzle Time
HAMWORK 8.4 Start Thinking! For use before Activity 8.4
