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Maths Quiz for Class 8 Linear Equations |
In this post, we are providing 20 online maths quiz
questions for class 8 linear equations. Online maths quiz will take around 20
minutes to complete it.
Question 1: Solve 5x + 9 = 39.
A) x = 8
B) x = 7
C) x = 6
D) x = 5
Explanation: 5x + 9 = 39 => 5x = 39 – 9 => 5x = 30 => x = 30/5 => x = 6
Question 2: Solve 4x – 3 = 2x + 5.
A) x = 4
B) x = 5
C) x = 6
D) x = 2
Explanation: 4x – 3 = 2x + 5 => 4x – 2x = 5 + 3 => 2x = 8 => x = 8/2 => x = 4
Question 3: Solve 6(x + 1) = 4(x + 4).
A) x = 5
B) x = 7
C) x = 8
D) x = 9
Explanation: 6(x + 1) = 4(x + 4) => 6x + 6 = 4x + 16 => 6x – 4x = 16 – 6 => 2x = 10 => x = 10/2 => x = 5
Question 4: Solve 3x/5 + 1/5 = 3/10.
A) x = 6
B) x = 1/6
C) x = 1/10
D) x = 10
Explanation: 3x/5 + 1/5 = 3/10 => 3x/5 = 3/10 – 1/5 => 3x/5 = 3/10 – 2/10 => 3x/5 = 1/10 => x = 1/10 × 5/3 => x = 1/6
Question 5: Solve the following linear equation: 3x + 7/3 = 17/3 – 2x
A) x = 1/3
B) x = 2/3
C) x = 1/2
D) x = 3/2
Explanation: 3x + 7/3 = 17/3 – 2x => 3x + 2x = 17/3 – 7/3 = 5x = 10/3 => x = 10/15 => x = 2/3
Question 6: Solve the following linear equation: 4x/9 = 8/27
A) x = 1/3
B) x = 3/2
C) x = 2/3
D) x = 1/2
Explanation: 4x/9 = 8/27 => x = 8/27 × 9/4 => x = 2/3
Question 7: Four times a number decreased by 7 gives the result 25. Find the number.
A) 7
B) 8
C) 9
D) 10
Explanation: Let the number be x. Then, 4x – 7 = 25 => 4x = 25 + 7 => 4x = 32 => x = 32/4 => x = 8. Thus, the number is 8.
Question 8: The sum of three consecutive positive integers is 90. Find the consecutive integers.
A) 30, 31, 32
B) 27, 28, 29
C) 28, 29, 30
D) 29, 30, 31
Explanation: Let the three positive consecutive integers be x, x + 1 and x + 2. Then, x + x + 1 + x + 2 = 90 => 3x + 3 = 90 => 3x = 90 – 3 => 3x = 87 => x = 87/3 => x = 29. Thus, the three consecutive integers are 29, 30, 31.
Question 9: The sum of two numbers is 68. If one number
exceeds the other by 22, find the two numbers.
A) 23 and 45
B) 22 and 23
C) 23 and 25
D) 24 and 45
Explanation: Let one number be x. Then, the other number is x + 22. According to the question, x + x + 22 = 68 => 2x + 22 = 68 => 2x = 68 – 22 => 2x = 46 => x = 46/2 => x = 23. Thus, the numbers are 23 and (23 + 22), that is, 23 and 45.
Question 10: The length of a rectangle is twice its breadth. If its perimeter is 96 cm, then find its breadth.
A) 14 cm
B) 15 cm
C) 16 cm
D) 32 cm
Explanation: Let the breadth of the rectangle be x cm. Then, the length is 2x cm. Perimeter of the rectangle = 2(length + breadth) => 96 = 2(2x + x) => 96 = 6x => x = 96/6 => x = 16. Thus, the breadth is 16 cm.
Question 11: If the sum of three consecutive even numbers 117, then find the numbers.
A) 35, 37, 39
B) 37, 39, 41
C) 39, 41, 43
D) 41, 43, 45
Explanation: Let the three consecutive numbers be x, x + 2 and x + 4. Then, x + x + 2 + x + 4 = 117 => 3x + 6 = 117 => 3x = 117 – 6 => 3x = 111 => x = 111/3 => x = 37. Thus, the numbers are 37, 39 and 41.
Question 12: Eighteen years from now, Neha’s age will be three times her present age. What is her present age?
A) 8 years
B) 9 years
C) 10 years
D) 11 years
Explanation: Let Neha’s present age be x years. Then, the age after 18 years = (x + 18) years. Thus, x + 18 = 3x => 3x – x = 18 => 2x = 18 => x = 18/2 => x = 9. Thus, Neha’s present age is 9 years.
Question 13: Solve: x/2 – x/4 = 1
A) x = 4
B) x = 3
C) x = 2
D) x = 8
Explanation: x/2 – x/4 = 1 => (2x – x)/4 = 1 => x/4 = 1 => x = 4
Question 14: Solve: (3x – 2)/(3x + 1) = (4x + 1)/(4x – 1)
A) x = 1/7
B) x = 1/16
C) x = 18
D) x = 1/18
Explanation: (3x
– 2)/(3x + 1) = (4x + 1)/(4x – 1) => (3x – 2) × (4x – 1) = (4x + 1) × (3x + 1) => 12x2 – 3x – 8x + 2 =
12x2 + 4x + 3x + 1 => 12x2 –11x + 2 = 12x2 +
7x + 1 => 12x2 – 12x2 – 11x – 7x = 1 – 2 => –18x = –1
=> 18x = 1 => x = 1/18
Question 15: Solve: (4 – x)/(x – 3) = 5/9
A) x = 53/14
B) x = 51/13
C) x = 51/14
D) x = 50/14
Explanation: (4 – x)/(x – 3) = 5/9 => 9(4 – x) = 5(x – 3) => 36 – 9x = 5x – 15 => 36 + 15 = 5x + 9x => 51 = 14x => x = 51/14
Question 16: Heena is 6 years younger than his brother Rohan. If the sum of the ages of Heena and Rohan is 26 years, find the age of Rohan.
A) 10 years
B) 16 years
C) 12 years
D) 14 years
Explanation: Let the age of Rohan be x years. Then, the age of Heena = (x – 6) years. Now, x + (x – 6) = 26 => x + x – 6 = 26 => 2x – 6 = 26 => 2x = 26 + 6 => 2x = 32 => x = 32/2 => x = 16 years
Question 17: The denominator of a fraction is 2 more than its numerator. If 1 is added to its numerator and its denominator, then the fraction becomes 1/2. Find the fraction.
A) 1/3
B) 1/2
C) 1/4
D) 1/5
Explanation: Let the numerator of the fraction be x. Then, its denominator = x + 2. Now, the fraction is x/(x + 2). According to condition, (x + 1)/(x + 2 + 1) = ½ => (x + 1)/(x + 3) = ½ => 2x + 2 = x + 3 => 2x – x = 3 – 2 => x = 1. Thus, fractions = 1/3
Question 18: I think of a number, halve it and the result is 8. Find the number I thought of.
A) 14
B) 15
C) 16
D) 18
Explanation: Let the number I thought of be x. Then, x/2 = 8 => x = 16. Thus, the number is 16.
Question 19: The length of a rectangle is 5 cm more than its breadth. If the perimeter of the rectangle is 50 cm, find the breadth of the rectangle.
A) 15 cm
B) 10 cm
C) 5 cm
D) 25 cm
Explanation: Let the breadth of the rectangle be x. Then, the length = x + 5. Perimeter of the rectangle = 2(l + b) => 50 = 2(x + 5 + x) => 50/2 = (x + 5 + x) => 25 = 2x + 5 => 2x = 25 – 5 => 2x = 20 => x = 20/2 => x = 10. Thus, the breadth of the rectangle is 10 cm.
Question 20: The sum of the digits of a 2-digit number is 15. The number formed by reversing its digits is 9 less than the original number. Find the original number.
A) 47
B) 67
C) 87
D) 96
Explanation: Let the ones digit of the number be x. Then, the tens digit = 15 – x. Now, the number = 10(15 – x) + x = 150 – 10x + x = 150 – 9x. The number after reversing its digits = 10x + 15 – x = 9x + 15. According to the condition, 9x + 15 = 150 – 9x – 9 => 9x + 9x = 150 – 9 – 15 => 18x = 126 => x = 126/18 => x = 7. Thus, the ones digit is 7 and the tens digit is 15 – 7, that is, 8. Therefore, the number is 87.
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