Class 8 Maths Liner Equation in one Variable Important Questions

Q 1 – Solve for x : 0.35x – 0.025 = 0.32x + 0.023

Given 0.35x – 0.025 = 0.32x +0.023

0.35x – 0.32x = 0.023 + 0.025

0.03x = 0.048

x = 0.048/0.03 = 1.6

 Q 2 – The sum of the two consecutive odd numbers is 36. Find the larger number.

Let the two consecutive odd numbers be x and x + 2.

Given that Sum of 2 consecutive odd numbers = 36.

x + x + 2 = 36

2x  + 2 = 36

2x = 34

x = 17

Then the other number = x + 2

                                        = 17 + 2

                                       = 19.


Therefore the integers are 17 and 19.

 Q 3 – The sum of a two-digit number and the number obtained by reversing its digits is 121.
Find the number if its unit place digit is 5.

Given units digit is x and tens digit is y

Hence the two digit number = 10y + x

Number obtained by reversing the digits = 10x + y

Given that sum of a two digit number and the number obtained by reversing the order of its digits is 121.

Then (10y+x)+(10x+y)=121

⇒10y+x+10x+y=121

⇒11x+11y=121

⇒x+y=11

Thus the required linear equation is x + y = 11.

x given (unit place) = 5

putting 5 in equation:- 5 + y = 11

Hence y = 6

x = 5 y = 6

Required number is = 56

Q 4 – A road divider of certain length is painted one–sixth yellow, three–fifth black and there remaining 28m is painted white. Find the length of the divider.

Let total length of pencil be x cm.

Then, black part = x/8

Remaining part pencil after black part = x – x/8 = 7x/8

then White part = 1/2 (7x/8)  

= 7x/16

Now Remaining part of pencil is blue = total length of pencil – (length of black part + length of white part)

length of blue part of pencil = x – (x/8 + 7x/16)

length of blue part of pencil = x – (2x + 7x)/16

length of blue part of pencil = x – 9x/16

length of blue part of pencil = (16 x – 9x)/16

∴ Length of blue part = 7x/16;

According to question

Length of blue part = 31/2  

7x/16 = 31/2  

⇒ 7x/16 = 7/2

⇒ x/16 = 1/2

⇒ x = 16/2

∴ x = 8 cm

 Q 5 – A boy gets 3 marks for each correct sum and loses 1 mark for each incorrect sum. He does 25 sums and obtains 67 marks. Then how many correct sums were there?

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 Q 6 – Ram and Mohan have Rs 60000 together. If Ram has Rs 8000 more than Mohan, then find how much money Ram has?

Let the amount with Rahim be x So, the amount with Ram is x + 8000 x+8000 ∴ X + x + 8000 = 60 , 000 ∴X+x+8000=60,000 ⇒ x = 26 , 000 ⇒x=26,000 ∴ ∴ The amount with Ram = 8000 + 26 , 000 = R s 34 , 000

Q 7 – I have Rs 1000 in ten and five rupee notes. If the number of ten rupee notes that I have is
ten more than the number of five rupee notes, how many notes do I have in each denomination?
.

Let no. of five rupee notes = x
no. of ten rupee notes = x+10

Cost of 5 rupee notes = Rs. 5x
Cost of 10 rupee notes = Rs. 10x +100
Total Cost = Rs. 1000

Therefore,

5x + 10x + 100 = 1000
15x = 1000 – 100
15x = 900
x = 900/15 = 60

Therefore, No. of five rupee  notes = 60
No. of ten rupee notes = 60 + 10 = 70

 Q 8 – If the side of chess board is smaller than its perimeter by 21 cm, then find the side of the
chess board.

If the side of a chess board is smaller than its

perimeter by 21 cm, then find the side of the chess

board.

P – s = 21

4s – s = 21

S = 7

Q 9 – Find the value of x in the equation 

Q 10 – If then what would be the value of y?

 Q 11 – Solve for 

 Q 12 – The angles of a triangle are in the ratio 2 : 3 : 4. Find the angles of the triangle.

It is given that the angle of triangle are in the ratio 2 : 3 : 4. Let the angles are 2x, 3x and 4x.

According to the angle sum property, the sum of interior angles of a triangle is 180 degree.

The value of x is 20.

Therefore the angles of triangle are  40, 60 and 80.

Q 13 – If the sum of two consecutive numbers is 11, find the numbers.

According to the problem

Let the two consecutive integers are  and .

so,

The first integer is and second integer is 

Q 14 – The difference between two positive numbers is 40 and the ratio of these integers is 1: 3. Find the integers.

Let two numbers are x and y .

According to question ,

y – x = 40…… (i)

x/y = 1/3.

or , y = 3x….. (ii)

Put the value of y from equation (ii) on the equation (i).

3x-x=40.

or , 2x=40.

or , x = 20.

So , y = 3*x

or , y = 3 * 20.

or , y =  60.

The integers are 60 and 20.