NCERT Class 7 Mathematics

PERIMETER AND AREA 219 7.0 cm 14.0 cm 44.0 cm^44 14 =3.14 10.5 cm 21.0 cm 66.0 cm^66 21 =3.14 21.0 cm 42.0 cm 132.0 cm 132 ...

220 MATHEMATICS EXAMPLE 12 What is the circumference of a circle of diameter 10 cm (Take π = 3.14)? SOLUTION Diameter of the cir ...

PERIMETER AND AREA 221 EXAMPLE 16 Sudhanshu divides a circular disc of radius 7 cm in two equal parts. What is the perimeter of ...

222 MATHEMATICS As done above if we divide the circle in 64 sectors, and arrange these sectors. It gives nearly a rectangle (Fig ...

PERIMETER AND AREA 223 SOLUTION (a) Radius of the larger circle = 10 cm So, area of the larger circle =πr^2 = 3.14 × 10 × 10 = 3 ...

224 MATHEMATICS A circle of radius 2 cm is cut out from a square piece of an aluminium sheet of side 6 cm. What is the area of ...

PERIMETER AND AREA 225 But when we convert a unit of area to a larger unit, the number of larger units will be smaller. For exam ...

226 MATHEMATICS Therefore, cost of cementing 1 m^2 = Rs 250 10 So, cost of cementing 1900 m^2 = Rs 250 10 × (^1900) = Rs 47,500 ...

PERIMETER AND AREA 227 Two cross roads, each of width 10 m, cut at right angles through the centre of a rectangular park of len ...

228 MATHEMATICS WHAT HAVE WE DISCUSSED? Perimeter is the distance around a closed figure whereas area is the part of plane occu ...

12.1 INTRODUCTION We have already come across simple algebraic expressions like x + 3, y– 5, 4x + 5, 10 y – 5 and so on. In Clas ...

230 MATHEMATICS (Later, when you study the chapter ‘Exponents and Powers’ you will realise that x^2 may also be read as x raised ...

ALGEBRAIC EXPRESSIONS 231 We can represent the terms and factors of the terms of an expression conveniently and elegantly by a t ...

232 MATHEMATICS SOLUTION S. No. Expression Term (which is not Numerical a Constant) Coefficient (i) xy + 4 xy 1 (ii) 13 – y^2 – ...

ALGEBRAIC EXPRESSIONS 233 hence they are like terms. On the other hand the terms 2xy and –3x, have different algebraic factors. ...

234 MATHEMATICS (iv) 3 xy 3,x,y Different Unlike The variable y is only 3 x 3,x in one term. (v) 6 xy^2 6,x,y,y Different Unlike ...

ALGEBRAIC EXPRESSIONS 235 (g) 3 4 x + 1 4 (h) 0.1 p (^2) + 0.2 q 2 Identify the numerical coefficients of terms (other than con ...

236 MATHEMATICS marbles and Ameena’s marbles, and to this sum add 3, that is, we take the sum of x,x+ 10 and 3. Ramu’s father’s ...

ALGEBRAIC EXPRESSIONS 237  Let us subtract 4n from 7n. 7 n – 4n = (7 × n) – (4 × n) = (7 – 4) × n = 3 × n = 3n or 7 n – 4n ...

238 MATHEMATICS  Subtracta – b from 3a – b + 4 The difference = 3a – b + 4 – (a – b) =3a – b + 4 – a + b Observe how we too ...