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Test: Linear Equations- 2

20 Questions MCQ Test Mathematics (Maths) Class 8 | Test: Linear Equations- 2

Description

Attempt Test: Linear Equations- 2 | 20 questions in 20 minutes | Mock test for Class 8 preparation | Free important questions MCQ to study Mathematics (Maths) Class 8 for Class 8 Exam | Download free PDF with solutions

QUESTION: 1

Solve: 4y = 20

A.
5
B.
16
C.
4
D.
24

Solution: 4y = 20 y = 20/4 y = 5

QUESTION: 2

Solve: 3x = 2x+ 18

A.
9
B.
6
C.
0
D.
18

Solution: 3x=2x+18 3x-2x=18 (transposing) x= 18

QUESTION: 3

Solve: x = 4/5(x+10)

A.
20
B.
10
C.
40
D.
30

Solution:

x = 4/5*(x + 10)

=> x = 4x/5 + 8

=> x - 4x/5 = 8

=> (5x - 4x)/5 = 8

=> x = 8 * 5 = 40

Verification / Checking-

LHS = x = 40

RHS = 4/5*(x + 10) = 4/5*(40 + 10) = 4/5 * 50 = 40

QUESTION: 4

The sum of three consecutive multiples of 7 is 357. Find the smallest multiple.

A.
112
B.
126
C.
119
D.
116

Solution:

Given,

Sum of multiples of 7 = 357

Let the numbers be x, x + 7 , x + 14

ATP,

x + x + 7 + x + 14 = 357

3x + 21 = 357

3x = 357 - 21

3x = 336

x = 336/3

x = 112

Therefore,

the numbers are 112, 119, 136

QUESTION: 5

In an equation the values of the expressions on the LHS and RHS are _______.

A.
different
B.
not equal
C.
equal
D.
none of these

Solution:

QUESTION: 6

The sum of two digit number and the number formed by interchanging its digit is 110. If ten is subtracted from the first number, the new number is 4 more than 5 times of the sum of the digits in the first number. Find the first number.

A.
46
B.
48
C.
64
D.
84

Solution:

Let the unit digit be y & tens digit be x.

Original number = (10x+y)

After interchanging the digits

New number = (10y+x)

(10x+y) + (10y+x) = 110

11x +11y = 110

11(x+y)= 110

x+y = 110/11

x+y= 10 (1)

x= 10-y (2)

(10x+y) - 10 = 4+ 5(x+y)

(10x+y) - 10 = 4+ 5(10)

(10x+y) = 4+ 50+10

(10x+y) = 64

10(10-y) +y = 64

100-10y +y= 64

100 -9y = 64

-9y = 64-100

-9y = -36

y= 36/9= 4

y= 4

putting the value of y in eqn 2

x= 10-y

x= 10-4

x= 6

Hence , the first number is 6 & second number is 4.

Original Number is 10x+y = 10* 6+4= 60+4= 64

QUESTION: 7

Solve: x − 2 = 7

A.
-5
B.
5
C.
9
D.
none of these

Solution:

QUESTION: 8

Solve: 5t – 3 = 3t – 5

A.
-1
B.
1
C.
0
D.
2

Solution:

5t-3=3t-55t-3t=-5+32t=-2 which gives t=-1

QUESTION: 9

What will be the solution of these equations ax+by = a-b, bx-ay = a+b

A.
x = 1, y = 2
B.
x = 2,y = -1
C.
x = -2, y = -2
D.
x = 1, y = -1

Solution:

ax+by=a-b
ax=a-b-by
x=(a-b-by)/a
bx-ay=a+b
substituting
b((a-b-by)/a)-ay=a+b
(ab-b²-b²y-a²y)/a=a+b
ab-b²-(b²+a²)y=a²+ab
-(b²+a²)y=a²+ab-ab+b²
y=-(a²+b²)/(a²+b²)
y= -1
substituting value of y
x=(a-b-b(-1))/a
x=a/a
x=1

QUESTION: 10

The present age of Sahil’s mother is three times the present age of Sahil. After 5 years their ages will add to 66 years. Find their present ages.

A.
28 years, 42 years
B.
14 years, 56 years
C.
28 years, 56 years
D.
14 years, 42 years

Solution:

Let present age of sahil is 'x'

his mother age is '3x'

after five yearssahil's age is 'x+5'

his mother's age is '3x+5'

according to problem, given sum of their ages after five years is 66

⇒(x+5)+(3x+5)=66

4x+10=664x=66-10

4x=56

x=56/4

x=14sahil's age is x=14=14 years

sahil's mother age is 3x=3(14)= 42=42 years.

QUESTION: 11

Amina thinks of a number and subtracts 5/2 from it. She multiplies the result by 8. The result now obtained is 3 times the same number she thought of. What is the number?

A.
2
B.
3
C.
4
D.
none of these

Solution:

Let she thoughts the no x

according to question ,she subtract the 5/2 from the no.= x-5/2

now ,she multiply the result by 8 =8(x-5/2)

according to statement

3x = 8(x-5/2)

3x=8x -20

20=5x

x=4

she thought the no. as 4

QUESTION: 12

Solve: 7x = 21

A.
3
B.
2
C.
14
D.
none of these

Solution:

QUESTION: 13

Solve: 5x+ 9 = 5 + 3x

A.
-2
B.
-1
C.
2
D.
none of these

Solution:

QUESTION: 14

Solve: y + 3 = 10

A.
13
B.
7
C.
-7
D.
none of these

Solution:

y + 3 = 10
y = 10 - 3
y = 7

QUESTION: 15

Sum of two numbers is 95. If one exceeds the other by 15, find the numbers.

A.
40 and 60
B.
50 and 55
C.
50 and 60
D.
40 and 55

Solution:

Let the number be x.
So, the other number is (x + 15).
(x + 15) + x = 95
2x + 15 = 95
2x = 95 - 15
2x = 80
x = 40
So, the numbers are 40 and 55.

QUESTION: 16

The value of the expression on one side of the equality sign is _____ to the value of the expression on the other side.

A.
different
B.
not equal
C.
equal
D.
none of these

Solution:

This says that any given equation says that it’s LHS is equal to RHS.

QUESTION: 17

A.
4
B.
8
C.
10
D.
6

Solution: 2x/3 + 1 = 7x/15 + 3 => 2x/3 -- 7x/15 = 3 -- 1 => 10x -- 7x/15 = 2 => 3x/15 = 2 => 3x = 2 × 15 => 3x = 30 => x = 30/3 => x = 10

QUESTION: 18

Solve: 5a = 30

A.
25
B.
35
C.
5
D.
6

Solution:

QUESTION: 19

Arjun is twice as old as Shriya. Five years ago his age was three times Shriya’s age. Find their present ages.

A.
15 years, 20 years
B.
10 years, 25 years
C.
10 years, 20 years
D.
None of these

Solution:

Let Arjun's age be x and shriya's age be y

A.T.Q.

x=2y

x-5=3 (y-5)

=>x-5=3y-15

=>2y-3y=-15+5

=>-y=-10

=>y=10

Now ,

x=2y

=>x=(2x10)

=>x=20

Therefore Arjun's age is 20 yrs and Shriya's age is 10 yrs.

QUESTION: 20

8 men and 12 boys can finish a piece of work in 10 days while 6 men and 8 boys can finish the work in 14 days. find the time taking by 1 man alone and 1 boy alone to finish the same work.