Mathematics

  Class 8 Ch- 13 Assignment 2 1.  Use the method of substitution to solve each other of the pair of simultaneous equations:   (a) x + y = 15            x - y = 3  (b) x + y = 0             x - y = 2  (c) 2x - y = 3            4x + y = 3  (d) 2x - 9y = 9       5x + 2y = 27 2.  Solve each other pair of equation given below using elimination method:  (a) x + 2y = -4             3x - 5y = -1  (b) 4x + 9y = 5            -5x + 3y = 8  (c) 9x - 6y = 12            4x + 6y = 14  (d) 2y - (3/x) = 12              5y + (7/x) = 1 Answers: 1.  (a) x = 9, y = 6 (b) x = 1, y = -1 (c) x = 1, y = -1 (d) x = 261/49, y = 9/49 2.  (a) x = -2, y = -1 (b) x = -1, y = 1 (c) x = 2, y = 1 (d) x = -1/2, y = 3

 

Ex 18.2 Q1. No. of degrees per desert chosen = 360 /40 = 9 ICe cream = 9 X 9 = 81 degree Cheese cake = 12 X 9 = 108 degree Pavlova = 5 X 9 = 45 degree Fruit salad = 8 X 9 = 72 degree None = 6 X 9 = 54 degree b) Percentage of none = 6/40 X 100% = 15% Q2. No. of degree per day = 360/60 =6 Monday = 5 X6 = 30 degree Tuesday = 8 X6 = 48 degree Wednesday =14 X6 = 84 degree Thursday = 6X 6 = 36 degree Friday = 27 X6 =162 degree a) Total student = 60 c) 5/60 = 1/12 HW Complete Ex 18.2 and 18.3  

  Ch=19 Revision Practice book Q1.a) Monday = 20cDs b) Tuesday = 15 c) 25 Cd d) 170 CDs Q3. a) 9 paintings b) 15-3 = 12 c) 12+ 9+ 15+3+4 = 43 Q5. 1 PEn = 4 pens Total = 13 X 4 = 52 pens Ex 19.2 Q1. a) Rugby b) Football c) Basket ball and Hockey d) There are total 100 boys and 50% of them like Rugby So, the no of boys who like Rugby = 50 Q2. a) Football b) Netball c) Rounders and Hockey d) As we dont have any data regarding no. of total girls , so we cant tell how many girls preferred football. Q3. Total no. of TVs= 40 Tvs No. of degrees per Tv = 360 / 40 = 9 degree No. of degrees for Panasonic = 18 X 9 = 162 degree Samsung = 12 X 9 = 108 degree Logik = 2 X9 = 18 degre Philips = 8 X9 = 72 degree Q4.No of degrees per Snack = 360/ 90 = 4 Crisps = 35 X4 = 140 degrees Nut = 20 X 4 = 80 degree Chocolate = 27X 4= 108 degree OTher = 8 X 4 = 32 degree

  Class 8 Ch 13 Assignment Q1. Solve for x: a) 3 (x+2) = x-1 Ans:- x= -7/2 = -3.5 b) 4x+ 3= 23-x Ans:- x= 4 c) 3x+2 = x+ 14 Ans:- x= 6 3x-x = 14 -2 2x = 12 x= 12/2 = 6 x=6 d) 8 (x-4) +4(5-x) = 0 Ans:- x= 3 8x - 32 + 20 - 4x =0 4x -12 = 0 4x = 12 x = 12/4 = 3 x=3 Q2. Two numbers are 5 (x+5) and 3(x-2). a) The sum of the numbers is 3. Write down the equation to show this. Ans:- 5 (x+5) + 3 (x-2) = 3 b) Solve the equation. Ans:- 5x +25 +3x - 6 =3 8x +19=3 8x = 3-19 8x = -16 x = -2 c) Find the two numbers. 5 ( -2 +5) = 5 X3 = 15 3 (-2-2) = 3 X -4 = -12 So, the numbers are 15 and -12 Q3. The length of one side of a rectangle is a cm. Another side is 3 (a-2) cm long. The perimeter is 44 cm. a) Write an equation to show this. Ans:- Perimeter = 2 (L+B) 2( a+ 3 (a-2) ) =44 2(a+3a-6) = 44 2(4a-6) =44 4a-6 = 22 4a = 22+6 =28 4a = 28 a = 28/4 = 7 b) Find the lengths of the side of the rectangle. Sides = a = 7cm 3 (a-2) = 3 (7-2) = 3 X 5 = 15cm Q4. Oditi thinks of a number. He doubles the number