Page 390 - Start Up Mathematics_8 (Non CCE)

7. 3 3 3. 65,000 cm 2
3 4 3 4 4. To find the area of a regular or irregular polygon, we
2 2 2 2 divide it into triangles, trapeziums, parallelograms, etc.
and find the area of each figure. The area of the polygon
3 is equal to the sum of these areas.

4 5. 36 M
Chapter 17 Let’s Evaluate
2
Puzzle 1. 2,42,000 m , ` 60,50,000
By placing three coins inside each of five rectangles and all 2. Base = 15 m, Height = 20 m 3. 24 m 4. 3 : 2
2
these five rectangles inside a bigger rectangle. 5. 14 cm 6. 36 m 7. Diagonal 8 m, side 5 m
2
Exercise 17.1 8. 3,000 cm 9. 5 m 10. 5 m
2
2
1. 456.75 cm 2. 42 cm 3. Decreases by 25% 11. ABQP = 69 cm , BCRQ = 57 cm , CDSR = 69 cm ,
2
2
2
5 2 2
2
4. 244 m 5. 8 2 cm or 11.31 cm ADSP = 57 cm 12. 45.5 cm
14
6. 16 : 25 7. 3,300 tiles Thinking Skills
2
8. 114 m 9. 5 m 1. 1 x 4a - x 2
2
Puzzle 2 1
I currently have one piece of chocolate, while I require 2. 0.215 cm 2 (Hint: Area of each sector = 4 r p 2 )
2 × 8 = 16 pieces. Every time I break the bar, I will get one 3. 16
more piece. Thus, I need to break the bar 16 – 1 = 15 times. Exemplar Problems
Exercise 17.2 1. a 2. c 3. 4 times 4. False
2
2
1. (a) 140 cm (b) 55 cm 2. 1,644 cm 2 1
2
3. 14 cm 5. 2 min or 30s 6. 1,050 m 7. 10 m
P A
2
4. 128 cm (Hint: , TM = NR = 6 cm. Chapter 18
T M N R
22 cm Exercise 18.1
By Pythagoras theorem PM = AN = 8 cm) 1. (a) 1,440 cm (b) 8.32 m 3
3
2
2
5. 2.1 m 6. 347 cm 7. 45 cm, 75 cm 2. (a) 250.047 cm (b) 373.248 dm (c) 125 m 3
3
3
8. 167 cm 2
3
3. 0.975 m or 975 L
Exercise 17.3 4. The volume will change to 1 th of the original volume.
2
1. 91 cm 2. 87.5 cm 2 8
–6
3
2
3. (a) 448 cm (b) 54 cm 2 5. 1.5 × 10 m 6. 1,096 dm 7. 7,315 L
4. 486 cm 2 8. 2.5 cm 9. 216 10. 32
11. 8 : 1 12. 750 13. 36 cm
Review Exercises
3
Multiple Choice Questions 14. ` 2,620 15. 3,600 cm 16. 41 2 days
3
1. c 2. d 3. c 4. c 5. c Exercise 18.2
2
Solve Mentally 1. 57.24 m , 34.84 m 2
True or False 2. 13.42 cm
2
2
1. False 2. True 3. True 4. False 3. (a) 121.5 cm , 81 cm , 7.79 cm
2
2
Fill in the Blanks (b) 61.44 m , 40.96 m , 5.54 m
2
2
3 (c) 864 dm , 576 dm , 20.78 dm
1. Perimeter 2. 3. base 4. 13 2 2
2 (d) 13.5 dm , 9 dm , 2.60 dm
2
2
2
Answer in One Word or a Line 4. (a) 384 m (b) 96 dm (c) 150 cm (d) 216 m 2
3
3
3
1. Heron’s formula for area of triangle 5. (a) 27 cm (b) 343 m (c) 512 dm (d) 729 cm 3
abc+ + 6. 896 cm 2 7. ` 70.78 8. 64 : 125 9. ` 3,600
(– )(– )(– )a s b s c where s =
A = ss 2 3
2 10. 10 m 11. 9.9 m, 3,920.4 m 12. 3 : 2
1 13. 10 m × 15 m × 20 m 14. 3,000
2
2. Side of rhombus (x) = d + d 2 2
1
2
2 15. 200, 44,000 cm 16. ` 2,60,000
382