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rn Mathematics for Class 6 4, , EXAMPLE3. The diameter of a wheel of a car is 70 cm. Find the distance covered by tr, during the time in which the wheel makes 1000 revolutions., , Solution Radius of the wheel = . Gin = vbicm., , Circumference of the wheel = 2zr, =(2x 22 35) em = 220 cm = 2.20mi, , In 1 revolution, the wheel covers a distance equal to its circumference., distance covered by the wheel in 1 revolution = 2.20 m., , distance covered by the wheel in 1000 revolutions, = (2.20 x 1000) m = 2200 m = 2.2 km., , EXERCISE 21B, 1. Find the circumference of a circle whose radius is, (i) 28 cm (ii) 10.5 cm (iii) 3.5 m, 2. Find the circumference of a circle whose diameter is, (i) 14cm (ii) 35 em (iii) 10.5 m, 3. Find the radius of a circle whose circumference is 176 cm., 4. Find the diameter of a wheel whose circumference is 264 cm., , 5. Find the distance covered by the wheel of a car in 500 revolutions if the, wheel is 77 cm., , 6. The diameter of the wheel of a car is 70 cm. How many revolutions will it ma, , , , 1.65 km?, TE, AREA, AREA The measurement of the region enclosed by a plane figure is called, the figure, , STANDARD UNIT OF AREA We say that the area of a Square of side 1 cm is, 1 square centimetre, written as1 cm’. The standard unit of area iscm?., , NOTE Ifa figure contains n squares, each of side 1 cm, we say that the, area of the figure is n cm”. ;, , EXAMPLE’. Consider the following regions:, , (i) (ii), , e (i) ABCD 1s a rectangle containing 5 x 3 = 15 squares, each having an are, , 1 figur, area of rectangle ABCD =15x1 cm? =15 cm’.