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Find the size of the angles marked with letters. 5. 6. a 108 0 b a y x a 40 0 70 0 7. 8. 35 0 x 57 0 9. 10. 28 0 5y 120 0 e 136 0 3y Scale drawing In representing real length of say, a plot whose dimensions are 16 m by 8 m, on paper, we use a scale. This means that a small length on paper represents a large length on ground. This representation is called a scale drawing of the real area. For example, the figure below is a scale drawing of a rectangular field whose measurements are 16 m by 8 m.
The measurements of the scale drawing are 8 cm by 4 cm. This means that 1 cm represents 2 m. This is the scale used to draw the plan of the field on paper. When making an accurate scale drawing, state what it is. Do not write any thing on the accurate diagram except letters marking points, as in your sketch. When asked for some particular length, the answer you give should be the actual length required and not the scaled length. Indicating scale There are 4 main ways of indicating the scale used. 1. Statement scale: 1 cm represents 100km is a statement of the scale that means 1 cm on the scale drawing represents 100 km on the ground. 2. Linear scale: A line is drawn and then divided into equal divisions, for example, divisions of 1 cm. see figure below. Against the linear scale the real distance on the ground is indicated, in this case kilometers. This means 5 cm on the map 400 represent 400 km on the ground, or 1 cm on the map represents = 80 km. 5 3. Ratio form: 1:100 means 1 cm represents 100 cm. The units in the scale in ratio form must be the same. 4. Representative fraction: (RF): A ratio scale such as 1:1000 may be written as a 1 representative fraction as . The units in the scale must be the same. 1000 One type of scale can be converted to another. Example A scale is given in statement form as 1 cm represents 3 km. write this scale in ratio form. Solution Scale in ratio form must have the same units. We therefore convert 3 km to centimeters. 3 km = 3 1000 100 = 300 000 cm. Therefore 1 cm represents 300 000 cm. In ratio form, the scale is 1:300 000. Example
Page 1 and 2: APPROXIMATIONS Rounding off Example
Page 3 and 4: Significant figures (sf) Significan
Page 5 and 6: Exercise 1. A man in Nairobi receiv
Page 7 and 8: 3. A radio that cost sh. 15 000 was
Page 9 and 10: 1 20000 ×1 2 × 21 Therefore, = sh
Page 11 and 12: 8. A business man had sh. 1 200 000
Page 13 and 14: 2. A dealer marks a price sh. 4 800
Page 15 and 16: (ii) income tax (sh.) 10 100 000 10
Page 17 and 18: (b) Express the total income tax fo
Page 19 and 20: O is at the vertex of the angle, an
Page 21 and 22: Exercise 1. In the figure shown, x
Page 23: t s 75 0 Solution s and 75 0 are ve
Page 27 and 28: 5. The floor of a school hall is re
Page 29 and 30: (i) Compass bearings On a compass,
Page 31 and 32: N A B 15km S 75 0 A Then we choose
Page 33 and 34: - We measure AB = 4.8cm. But 1cm re
Page 35 and 36: Types of polygons Name Number of si
Page 37 and 38: 50 0 +w +x = 180 0 50 0 + 50 0 + x
Page 39 and 40: (d) (e) Quadrilaterals These are fl
Page 41 and 42: n n-2 From the above table we see t
Page 43: 8. One of the large and one of the

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