Class 8 Ch 13 Assignment

 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. He adds 3. He doubles again. The answer is 70.

What number did he think off?

Ans:- LEt the number be x

2(2x +3 ) = 70

4x+ 6 = 70

4x = 70 -6= 64

4x = 64

x = 64/4 = 16

The number is 16 .

Q5. The first side of a triangle is b cm long.

The second side is twice as long as first side.

The third side is 5 cm longer than the second side.

a) The perimeter of the triangle is 1 metre.

Write an equation for the above.

b) Solve the equation.

C) Find the longest side of the triangle.

Ans:- First side = b cm

Second side = 2b cm

Third side = 2b +5 cm

PErimeter = 1m =100cm

b+ 2b+2b+5 = 100

5b +5 = 100

5b =100-6 =95

b = 19cm

The longest side = third side = 2 X19 +5 = 38 +5 = 43cm