Wednesday 24 February 2021

CBSE Class 8 Maths - MCQ and Online Tests - Unit 2 - Linear Equations in One Variable

CBSE Class 8 Maths – MCQ and Online Tests –  Unit 2 – Linear Equations in One Variable

Every year CBSE students attend Annual Assessment exams for 6,7,8,9,11th standards. These exams are very competitive to all the students. So our website provides online tests for all the 6,7,8,9,11th standards’ subjects. These tests are also very effective and useful for those who preparing for any competitive exams like Olympiad etc. It can boost their preparation level and confidence level by attempting these chapter wise online tests.

These online tests are based on latest CBSE syllabus. While attempting these, our students can identify their weak lessons and continuously practice those lessons for attaining high marks. It also helps to revise the NCERT textbooks thoroughly


 

CBSE Class 8 Maths – MCQ and Online Tests – Unit 2 – Linear Equations in One Variable

Question 1.
The root of the equation x – 8 = 2 is
(a) 2
(b) 8
(c) 6
(d) 10.

Answer

Answer: (d)
Hint:
x – 8 = 2 ? x = 2 + 8 = 10.


Question 2.
If two angles are complementary and one angle is 10° greater than the other, then the smaller angle of the two is
(a) 40°
(b) 50°
(c) 90°
(d) 180°.

Answer

Answer: (a)
Hint:
x° = (90° – x°) + 10°
? 2x° = 100° ? x° = 50°
? 90° – x° = 40°.


Question 3.
The root of the equation 3x + 8 = 14 is
(a) 1
(b) 2
(c) -1
(d) \(\frac{1}{2}\)

Answer

Answer: (b)
Hint:
3x + 8 = 14 ? 3x = 14 – 8 = 6
? x = \(\frac{6}{3}\) = 2.


Question 4.
The root of the equation 2y = 5(3 + y) is
(a) 5
(b) \(\frac{1}{5}\)
(c) -5
(d) –\(\frac{1}{5}\)

Answer

Answer: (c)
Hint:
2y = 5 (3 + y) ? 2y = 15 + 5y
? 5y – 2y = -15
? 3y = -15 ? y = –\(\frac{15}{3}\) = -5


Question 5.
The statement ‘on adding 10 in a number, the number becomes 20’ in the form of an equation is
(a) x – 10 = 20
(b) x + 10 = 20
(c) 10x = 20
(d) \(\frac{x}{10}\) = 20.

Answer

Answer: (b)
Hint:
Let the number be x.


Question 6.
If 9 is added to a number, it becomes 25. This statement in the form of an equation is
(a) x + 9 = 25
(b) x – 9 = 25
(c) 9x = 25
(d) \(\frac{x}{9}\) = 25.

Answer

Answer: (a)
Hint:
Let the number be x.


Question 7.
If 15 is subtracted from a number, it becomes -5. This statement in the form of an equation is
(a) x + 15 = -5
(b) x – 15 = 5
(c) x + 15 = 5
(d) x – 15 = -5.

Answer

Answer: (d)
Hint:
Let the number be x.


Question 8.
Seven times a number is 42. This statement in the form of an equation is
(a) x + 7 = 42
(b) 7x = 42
(c) \(\frac{x}{7}\) = 42
(d) x – 7 = 42.

Answer

Answer: (b)
Hint:
Let the number be x.


Question 9.
A number when divided by 5 gives 6. This statement in the form of an equation is
(a) x – 5 = 6
(b) x + 5 = 6
(c) \(\frac{x}{5}\) = 6
(d) 5x = 6.

Answer

Answer: (c)
Hint:
Let the number be x.


Question 10.
A number when subtracted from 40 results into 15. This statement in the form of an equation is
(a) 40 – x = 15
(b) x – 40 = 15
(c) 40 + x = 15
(d) 40x = 15.

Answer

Answer: (a)
Hint:
Let the number be x.


Question 11.
If 6 is added to 3 times of a number, it becomes 15. This statement in the form of an equation is
(a) 3x + 6 = 15
(b) 3x – 6 = 15
(c) 3x + 15 = 6
(d) \(\frac{3x}{6}\) = 15.

Answer

Answer: (a)
Hint:
Let the number be x.


Question 12.
On subtracting 30 from two times a number, we get 56. This statement in the form of an equation is
(a) 2x – 30 = 56
(b) 2x + 30 = 56
(c) 30 – 2x = 56
(d) \(\frac{30}{2x}\) = 56.

Answer

Answer: (a)
Hint:
Let the number be x.


Question 13.
The root of the equation z + 4 = -8 is
(a) 3
(b) -32
(c) 12
(d) 4.

Answer

Answer: (b)
Hint:
z + 4 = -8 ? \(\frac{z}{4}\) = -8
? z = 4 (-8) = -32.


Question 14.
The root of the equation 3x = \(\frac{20}{7}\) – x is
(a) 10
(b) \(\frac{20}{21}\)
(c) –\(\frac{5}{7}\)
(d) \(\frac{5}{7}\)

Answer

Answer: (d)
Hint:
3x = \(\frac{20}{7}\) – x ? 3x + x = \(\frac{20}{7}\)
? 4x = \(\frac{20}{7}\) ? x = \(\frac{20}{7×4}\) = \(\frac{5}{7}\)


Question 15.
The root of the equation 2x + 3 = 2(x – 4) is
(a) 2
(b) 4
(c) 0
(d) does not exist.

Answer

Answer: (d)
Hint:
2x + 3 = 2 (x – 4)
? 2x + 3 = 2x – 8
? 3 = -8 which is impossible.


Question 16.
x is an odd number. The largest odd number preceding x is
(a) x – 1
(b) x – 2
(c) x – 3
(d) x – 4.

Answer

Answer: (b)


Question 17.
The difference of two numbers is 21. The larger number is x. The smaller number is
(a) 21 + x
(b) 21 – x
(c) x – 21
(d) -x – 21.

Answer

Answer: (c)
Hint:
x – smaller number = 21
? smaller number = x – 21


Question 18.
In a two digit number, the unit’s digit is x and the ten’s digit is y. Then, the number is
(a) 10y + x
(b) 10x + y
(c) 10y – x
(d) 10x – y.

Answer

Answer: (a)
Hint:
Required number
= 10 × y + 1 × x = 10y + x.


Question 19.
When 9 is added to two times a number, we get 67. The number is
(a) 25
(b) 27
(c) 29
(d) 31.

Answer

Answer: (c)
Hint:
2x + 9 = 67 ? x = 29.


Question 20.
The root of the equation –\(\frac{5}{4x}\) = 15 is
(a) \(\frac{1}{12}\)
(b) –\(\frac{1}{12}\)
(c) \(\frac{1}{20}\)
(d) –\(\frac{1}{20}\)

Answer

Answer: (b)
Hint:
–\(\frac{5}{4x}\) = 15 ? x = –\(\frac{5}{4×15}\) = –\(\frac{1}{12}\)


Question 21.
The value of x in \(\frac{3}{4}\) x = 7 – x is
(a) 4
(b) 3
(c) \(\frac{7}{3}\)
(d) 7.

Answer

Answer: (a)
Hint:
\(\frac{3}{4}\) x = 7 – x ? \(\frac{3}{4}\) x + x = 7
? \(\frac{7}{4}\) x = 7 ? x = 4


Question 22.
\(\frac{3}{4}\) part of a number is 5 more than its \(\frac{2}{3}\) part. This statement in the form of an equation is
(a) \(\frac{2}{3}\) x – \(\frac{3}{4}\) x= 5
(5) \(\frac{2}{3}\) x – 5 =\(\frac{3}{4}\) x
(c) \(\frac{3}{4}\) x = \(\frac{2}{3}\) x + 5
(d) \(\frac{3}{4}\) x – 5 = –\(\frac{2}{3}\) x

Answer

Answer: (c)
Hint:
Let the number be x²


Question 23.
The value of x in –\(\frac{2}{3}\) = 2x is 3
(a) \(\frac{1}{3}\)
(b) –\(\frac{1}{3}\)
(c) 3
(d) – 3.

Answer

Answer: (b)
Hint:
–\(\frac{2}{3}\) = 2x ? x = –\(\frac{1}{3}\)


Question 24.
The root of the equation 5x – 8 = 7 is
(a) 1
(b) 2
(c) 3
(d) -3.

Answer

Answer: (c)
Hint:
5x – 8 = 7 ? 5x = 8 + 7 = 15
? x = \(\frac{15}{5}\) = 3.


Question 25.
The root of the equation x + 3 = 5 is
(a) 1
(b) 2
(0 -1
(d) -2.

Answer

Answer: (b)
Hint:
x + 3 = 5 ? x = 5 – 3 = 2.


Question 26.
The standard form of a linear equation in one variable x is
(a) ax + b = 0
(b) ax² + bx + c = 0
(c) ax³ + bx² + cx + d = 0
(d) ax4 + bx³ + cx² + dx + e = 0.

Answer

Answer: (a)


Question 27.
Of the following, the linear equation in one variable x, is
(a) \(\frac{4}{x}\) = \(\frac{x}{4}\)
(b) \(\frac{1}{x}\) + \(\frac{1}{x-1}\) = 1
(c) \(\frac{x}{2}\) + \(\frac{x}{3}\) + \(\frac{1}{4}\)
(d) x² + 2x + 3 = 0.

Answer

Answer: (c)


Question 28.
The degree of the equation x² – 2x + 1 = x² – 3 is
(a) 1
(b) 2
(c) 0
(d) 3.

Answer

Answer: (a)
Hint:
x² – 2x + 1 = x² – 3 ? 2x = 4


Question 29.
If two angles are supplementary and one angle is double the other, then the larger angle is
(a) 60°
(b) 90°
(c) 120°
(d) 180°.

Answer

Answer: (c)
Hint:
x° + 2x° = 180° ? 3x° = 180°
? x° = 60° ? 2x° = 120°


Question 30.
Twice a number is as much greater than 30 as the three times of the number less than 60. The number is
(a) 6
(b) 9
(c) 12
(d) 18.

Answer

Answer: (d)
Hint:
2x – 30 = 60 – 3x ? 5x = 90
? x = 18.


Question 31.
One number is greater than the other number by 3. The sum of two numbers is 23. The two numbers are
(a) 13, 10
(b) 14, 9
(c) 12, 11
(d) 15, 8.

Answer

Answer: (a)
Hint:
(x + 3) + x = 23 ? 2x = 20
? x = 10 ? x + 3 = 13


Question 32.
The root of the equation \(\frac{y}{3}\) – 7 = 11 is
(a) 54
(b) -54
(c) 18
(d) -18

Answer

Answer: (a)
Hint:
\(\frac{y}{3}\) – 7 = 11 ? \(\frac{y}{3}\) = 7 + 11 = 18
? y = 3 × 18 = 54


Question 33.
The root of the equation 14 – x = 8 is
(a) 2
(b) 4
(c) 6
(d) 8.

Answer

Answer: (c)
Hint:
14 – x = 8 ? x = 14 – 8 = 6


Question 34.
The root of the equation \(\frac{5x}{3}\) = 30 is
(a) 9
(b) 12
(c) 15
(d) 18

Answer

Answer: (d)
Hint:
\(\frac{5x}{3}\) = 30 ? 5x = 3 × 30 = 90
? x = \(\frac{90}{5}\) = 18


Question 35.
The root of the equation 3y + 4 = 5y – 4 is
(a) 1
(b) 2
(c) 3
(d) 4.

Answer

Answer: (d)
Hint:
3y + 4 = 5y – 4 ? 5y – 3y = 4 + 4
? 2y = 8 ? y = \(\frac{8}{2}\) = 4


Question 36.
The root of the equation \(\frac{7x}{3}\) = 3 is
(a) \(\frac{5x}{3}\)
(b) \(\frac{5x}{3}\)
(c) 3
(d) 7

Answer

Answer: (a)
Hint:
\(\frac{7}{x}\) = 3 ? 3x = 7 ? x = \(\frac{7}{3}\)


Question 37.
The root of the equation 3x + 4 = 13 is
(a) 1
(b) 2
(c) 3
(d) 4.

Answer

Answer: (c)
Hint:
3x + 4 = 13 ? 3x = 13 – 4 = 9
? x = \(\frac{9}{3}\) = 3


Question 38.
The root of the equation 9z – 15 = 9 – 3z is
(a) 1
(b) 2
(c) 3
(d) 4.

Answer

Answer: (b)
Hint:
9z – 15 = 9 – 3z ? 9z + 3z = 9 + 15
? 12x = 24 ? z = \(\frac{24}{12}\) = 2


Question 39.
The root of the equation \(\frac{4x}{7}\) – 12 = 0 is
(a) 7
(b) 14
(c) 21
(d) -21

Answer

Answer: (c)
Hint:
\(\frac{4x}{7}\) – 12 = 0 ? \(\frac{4x}{7}\) = 12
? 4x = 7 × 12 = 84
? x = \(\frac{84}{4}\) = 21


Question 40.
The root of the equation 3x = \(\frac{20}{7}\) – x is
(a) \(\frac{7}{5}\)
(b) \(\frac{5}{7}\)
(c) –\(\frac{7}{5}\)
(d) –\(\frac{5}{7}\)

Answer

Answer: (b)
Hint:
3x = \(\frac{20}{7}\) – x ? 3x + x = \(\frac{20}{7}\)
? 4x = \(\frac{20}{7}\) ? x = \(\frac{20}{7×4}\) = \(\frac{5}{7}\)


Question 41.
The root of the equation 2y = 5 (7 – y ) is
(a) 5
(b) -5
(c) 3
(d) -3.

Answer

Answer: (a)
Hint:
2y = 5(7 – y) ? 2y = 35 – 5y
? 2y + 5y = 35
? 7y = 35 ? y = \(\frac{35}{7}\) = 5


Question 42.
The root of the equation
(2x – 1) + (x – 1) = x + 2 is
(a) 1
(b) 2
(c) -1
(d) -2.

Answer

Answer: (b)
Hint:
(2x – 1) + (x – 1) = x + 2
? 2x = 4 ? x = \(\frac{4}{2}\) = 2.


Question 43.
The root of the equation
13x – 14 = 9x + 10 is
(a) 1
(b) 2
(c) 3
(d) 6.

Answer

Answer: (d)
Hint:
13x – 14 = 9x + 10 ? 13x – 9x = 10 + 14
? 4x = 24 ? x = \(\frac{24}{4}\) = 6


Question 44.
The root of the equation
11x – 5 – x + 6 = 2x + 17 is
(a) 1
(b) 2
(c) 3
(d) 4.

Answer

Answer: (b)
Hint:
11x – 5 – x + 6 = 2x + 17
? 8x = 16 ? x = 2.


Question 45.
The root of the equation \(\frac{2}{3}\) y = \(\frac{5}{12}\) is
(a) \(\frac{8}{5}\)
(b) \(\frac{5}{8}\)
(c) 5
(d) 8

Answer

Answer: (b)
Hint:
\(\frac{2}{3}\) y = \(\frac{5}{12}\)
? y = \(\frac{5}{12}\) × \(\frac{3}{2}\) = \(\frac{5}{8}\)


Question 46.
The root of the equation 7 (x – 1) = 21 is
(a) 1
(b) 2
(c) 3
(d) 4.

Answer

Answer: (d)
Hint:
7 (x – 1) = 21 ? x – 1 = \(\frac{21}{7}\) = 3
? x = 4.


Question 47.
The root of the equation \(\frac{3}{2}\) x = – 27 is
(a) 6
(b) 12
(c) 18
(d) -18

Answer

Answer: (d)
Hint:
\(\frac{5}{12}\) x = -27 ? x = –\(\frac{27×2}{3}\) = -18.


Question 48.
The solution of the equation \(\frac{5}{x}\) = 2 is
(a) 10
(b) \(\frac{2}{5}\)
(c) \(\frac{5}{2}\)
(d) \(\frac{1}{10}\)

Answer

Answer: (c)
Hint:
\(\frac{5}{x}\) = 2
? 2x = 5 ? x = \(\frac{5}{2}\)


Question 49.
The largest number of the three consecutive numbers is x + 1. Then, the smallest number is
(a) x + 2
(b) x + 1
(c) x
(d) x – 1.

Answer

Answer: (d)
Hint:
x – 1, x, x + 1


Question 50.
If x is an even number then the consecutive even number is
(a) x + 1
(b) x + 2
(c) 2x
(d) x – 1.

Answer

Answer: (b)


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