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15. Linear Inequations 
(Including Number Lines) 
Exercise 15 (A) 
Question 1. 
If the replacement set is the set of natural numbers, solve. 
(i) x – 5 < 0 
(ii) x + 1 < 7 
(iii) 3x – 4 > 6 
(iv) 4x + 1 > 17 
Solution: 
(i) x – 5 < 0 
x – 5 + 5 <0 + 5 ………(Adding 5) 
=> x < 5 
Required answer = {1, 2, 3, 4} 
(ii) x + 1 = 7 => x + 1 – 1 = 7 – 1 (Subtracting 1) 
=> x = 6 
Required answer = {1, 2, 3, 4, 5, 6} 
(iii) 3x – 4 > 6 
3x – 4 + 4 > 6 + 4 (Adding 4) 
=> 3x > 10 
 >  …(Dividing by 3) 
=> x >  
=> x >  
Required answer = { 4, 5, 6, …} 
(iv) 4x + 1 = 17 
=> 4x + 1 – 1 = 17 – 1 (Subtracting) 
=> 4x = 16 
=>  =  (Dividing by 4) 
=> x = 4 
Required answer = {4, 5, 6, …} 
Question 2. 
If the replacement set = {-6, -3, 0, 3, 6, 9}; find the truth set of the following: 
(i) 2x – 1 > 9 
(ii) 3x + 7 < 1 
Solution: 
(i) 2x – 1 > 9 
? 2x – 1 + 1 > 9 + 1 (Adding 1) 
? 2x > 10 
? x > 5 (Dividing by 2) 
? x > 5 
Page 2


15. Linear Inequations 
(Including Number Lines) 
Exercise 15 (A) 
Question 1. 
If the replacement set is the set of natural numbers, solve. 
(i) x – 5 < 0 
(ii) x + 1 < 7 
(iii) 3x – 4 > 6 
(iv) 4x + 1 > 17 
Solution: 
(i) x – 5 < 0 
x – 5 + 5 <0 + 5 ………(Adding 5) 
=> x < 5 
Required answer = {1, 2, 3, 4} 
(ii) x + 1 = 7 => x + 1 – 1 = 7 – 1 (Subtracting 1) 
=> x = 6 
Required answer = {1, 2, 3, 4, 5, 6} 
(iii) 3x – 4 > 6 
3x – 4 + 4 > 6 + 4 (Adding 4) 
=> 3x > 10 
 >  …(Dividing by 3) 
=> x >  
=> x >  
Required answer = { 4, 5, 6, …} 
(iv) 4x + 1 = 17 
=> 4x + 1 – 1 = 17 – 1 (Subtracting) 
=> 4x = 16 
=>  =  (Dividing by 4) 
=> x = 4 
Required answer = {4, 5, 6, …} 
Question 2. 
If the replacement set = {-6, -3, 0, 3, 6, 9}; find the truth set of the following: 
(i) 2x – 1 > 9 
(ii) 3x + 7 < 1 
Solution: 
(i) 2x – 1 > 9 
? 2x – 1 + 1 > 9 + 1 (Adding 1) 
? 2x > 10 
? x > 5 (Dividing by 2) 
? x > 5 
Required answer = {6, 9} 
(ii) 3x + 7 = 1 
? 3x + 7 – 7 = 1 – 7 (Subtracting 7) 
? 3x = – 6 
? x = – 2 
Required Answer = {-6, -3} 
Question 3. 
Solve 7 > 3x – 8; x ? N 
Solution: 
7 > 3x – 8 
=> 7 – 3x > 3x – 3x – 8 (Subtracting 3x) 
=> 7 – 7 – 3x > 3x – 3x – 8 – 7 (Subtracting 7) 
=> -3x > -15 
=> x < 5 (Dividing by -3) 
Required Answer = {1, 2, 3, 4} 
Note : Division by negative number reverses the inequality. 
Question 4. 
-17 < 9y – 8 ; y ? Z 
Solution: 
-17 < 9y – 8 
=> -17 + 8 < 9y – 8 + 8 (Adding 8) 
=> -9 < 9y 
=> -1 < y (Dividing by 9) 
Required number = {0, 1, 2, 3, 4, …} 
Question 5. 
Solve 9x – 7 = 28 + 4x; x ? W 
Solution: 
9x – 1 = 28 + 4x 
=> 9x – 4x – 7 = 28 + 4x – 4x (Subtracting 4x) 
=> 5x – 7 = 28 
=> 5x – 7 + 7 = 28 + 7 (Adding 7) 
=> 5x = 35 
=> x = 7 (Dividing by 5) 
Required answer = {0, 1, 2, 3, 4, 5, 6, 7} 
Question 6. 
Solve : x + 8 < 12 ; x ? W 
Page 3


15. Linear Inequations 
(Including Number Lines) 
Exercise 15 (A) 
Question 1. 
If the replacement set is the set of natural numbers, solve. 
(i) x – 5 < 0 
(ii) x + 1 < 7 
(iii) 3x – 4 > 6 
(iv) 4x + 1 > 17 
Solution: 
(i) x – 5 < 0 
x – 5 + 5 <0 + 5 ………(Adding 5) 
=> x < 5 
Required answer = {1, 2, 3, 4} 
(ii) x + 1 = 7 => x + 1 – 1 = 7 – 1 (Subtracting 1) 
=> x = 6 
Required answer = {1, 2, 3, 4, 5, 6} 
(iii) 3x – 4 > 6 
3x – 4 + 4 > 6 + 4 (Adding 4) 
=> 3x > 10 
 >  …(Dividing by 3) 
=> x >  
=> x >  
Required answer = { 4, 5, 6, …} 
(iv) 4x + 1 = 17 
=> 4x + 1 – 1 = 17 – 1 (Subtracting) 
=> 4x = 16 
=>  =  (Dividing by 4) 
=> x = 4 
Required answer = {4, 5, 6, …} 
Question 2. 
If the replacement set = {-6, -3, 0, 3, 6, 9}; find the truth set of the following: 
(i) 2x – 1 > 9 
(ii) 3x + 7 < 1 
Solution: 
(i) 2x – 1 > 9 
? 2x – 1 + 1 > 9 + 1 (Adding 1) 
? 2x > 10 
? x > 5 (Dividing by 2) 
? x > 5 
Required answer = {6, 9} 
(ii) 3x + 7 = 1 
? 3x + 7 – 7 = 1 – 7 (Subtracting 7) 
? 3x = – 6 
? x = – 2 
Required Answer = {-6, -3} 
Question 3. 
Solve 7 > 3x – 8; x ? N 
Solution: 
7 > 3x – 8 
=> 7 – 3x > 3x – 3x – 8 (Subtracting 3x) 
=> 7 – 7 – 3x > 3x – 3x – 8 – 7 (Subtracting 7) 
=> -3x > -15 
=> x < 5 (Dividing by -3) 
Required Answer = {1, 2, 3, 4} 
Note : Division by negative number reverses the inequality. 
Question 4. 
-17 < 9y – 8 ; y ? Z 
Solution: 
-17 < 9y – 8 
=> -17 + 8 < 9y – 8 + 8 (Adding 8) 
=> -9 < 9y 
=> -1 < y (Dividing by 9) 
Required number = {0, 1, 2, 3, 4, …} 
Question 5. 
Solve 9x – 7 = 28 + 4x; x ? W 
Solution: 
9x – 1 = 28 + 4x 
=> 9x – 4x – 7 = 28 + 4x – 4x (Subtracting 4x) 
=> 5x – 7 = 28 
=> 5x – 7 + 7 = 28 + 7 (Adding 7) 
=> 5x = 35 
=> x = 7 (Dividing by 5) 
Required answer = {0, 1, 2, 3, 4, 5, 6, 7} 
Question 6. 
Solve : x + 8 < 12 ; x ? W 
Solution: 
 
Question 7. 
Solve -5 (x + 4) > 30 ; x ? Z 
Solution: 
 
Question 8. 
Solve the inquation 8 – 2x > x – 5 ; x ? N. 
Solution: 
 
x = 1, 2, 3, 4 (x ? N) 
Solution set = {1, 2, 3, 4} 
Page 4


15. Linear Inequations 
(Including Number Lines) 
Exercise 15 (A) 
Question 1. 
If the replacement set is the set of natural numbers, solve. 
(i) x – 5 < 0 
(ii) x + 1 < 7 
(iii) 3x – 4 > 6 
(iv) 4x + 1 > 17 
Solution: 
(i) x – 5 < 0 
x – 5 + 5 <0 + 5 ………(Adding 5) 
=> x < 5 
Required answer = {1, 2, 3, 4} 
(ii) x + 1 = 7 => x + 1 – 1 = 7 – 1 (Subtracting 1) 
=> x = 6 
Required answer = {1, 2, 3, 4, 5, 6} 
(iii) 3x – 4 > 6 
3x – 4 + 4 > 6 + 4 (Adding 4) 
=> 3x > 10 
 >  …(Dividing by 3) 
=> x >  
=> x >  
Required answer = { 4, 5, 6, …} 
(iv) 4x + 1 = 17 
=> 4x + 1 – 1 = 17 – 1 (Subtracting) 
=> 4x = 16 
=>  =  (Dividing by 4) 
=> x = 4 
Required answer = {4, 5, 6, …} 
Question 2. 
If the replacement set = {-6, -3, 0, 3, 6, 9}; find the truth set of the following: 
(i) 2x – 1 > 9 
(ii) 3x + 7 < 1 
Solution: 
(i) 2x – 1 > 9 
? 2x – 1 + 1 > 9 + 1 (Adding 1) 
? 2x > 10 
? x > 5 (Dividing by 2) 
? x > 5 
Required answer = {6, 9} 
(ii) 3x + 7 = 1 
? 3x + 7 – 7 = 1 – 7 (Subtracting 7) 
? 3x = – 6 
? x = – 2 
Required Answer = {-6, -3} 
Question 3. 
Solve 7 > 3x – 8; x ? N 
Solution: 
7 > 3x – 8 
=> 7 – 3x > 3x – 3x – 8 (Subtracting 3x) 
=> 7 – 7 – 3x > 3x – 3x – 8 – 7 (Subtracting 7) 
=> -3x > -15 
=> x < 5 (Dividing by -3) 
Required Answer = {1, 2, 3, 4} 
Note : Division by negative number reverses the inequality. 
Question 4. 
-17 < 9y – 8 ; y ? Z 
Solution: 
-17 < 9y – 8 
=> -17 + 8 < 9y – 8 + 8 (Adding 8) 
=> -9 < 9y 
=> -1 < y (Dividing by 9) 
Required number = {0, 1, 2, 3, 4, …} 
Question 5. 
Solve 9x – 7 = 28 + 4x; x ? W 
Solution: 
9x – 1 = 28 + 4x 
=> 9x – 4x – 7 = 28 + 4x – 4x (Subtracting 4x) 
=> 5x – 7 = 28 
=> 5x – 7 + 7 = 28 + 7 (Adding 7) 
=> 5x = 35 
=> x = 7 (Dividing by 5) 
Required answer = {0, 1, 2, 3, 4, 5, 6, 7} 
Question 6. 
Solve : x + 8 < 12 ; x ? W 
Solution: 
 
Question 7. 
Solve -5 (x + 4) > 30 ; x ? Z 
Solution: 
 
Question 8. 
Solve the inquation 8 – 2x > x – 5 ; x ? N. 
Solution: 
 
x = 1, 2, 3, 4 (x ? N) 
Solution set = {1, 2, 3, 4} 
Question 9. 
Solve the inequality 18 – 3 (2x – 5) > 12; x ? W. 
Solution: 
 
Question 10. 
Solve :  + 15 < 17; x ? W. 
Solution: 
 
Question 11. 
Solve : -3 + x < 2, x ? N 
Solution: 
 
Page 5


15. Linear Inequations 
(Including Number Lines) 
Exercise 15 (A) 
Question 1. 
If the replacement set is the set of natural numbers, solve. 
(i) x – 5 < 0 
(ii) x + 1 < 7 
(iii) 3x – 4 > 6 
(iv) 4x + 1 > 17 
Solution: 
(i) x – 5 < 0 
x – 5 + 5 <0 + 5 ………(Adding 5) 
=> x < 5 
Required answer = {1, 2, 3, 4} 
(ii) x + 1 = 7 => x + 1 – 1 = 7 – 1 (Subtracting 1) 
=> x = 6 
Required answer = {1, 2, 3, 4, 5, 6} 
(iii) 3x – 4 > 6 
3x – 4 + 4 > 6 + 4 (Adding 4) 
=> 3x > 10 
 >  …(Dividing by 3) 
=> x >  
=> x >  
Required answer = { 4, 5, 6, …} 
(iv) 4x + 1 = 17 
=> 4x + 1 – 1 = 17 – 1 (Subtracting) 
=> 4x = 16 
=>  =  (Dividing by 4) 
=> x = 4 
Required answer = {4, 5, 6, …} 
Question 2. 
If the replacement set = {-6, -3, 0, 3, 6, 9}; find the truth set of the following: 
(i) 2x – 1 > 9 
(ii) 3x + 7 < 1 
Solution: 
(i) 2x – 1 > 9 
? 2x – 1 + 1 > 9 + 1 (Adding 1) 
? 2x > 10 
? x > 5 (Dividing by 2) 
? x > 5 
Required answer = {6, 9} 
(ii) 3x + 7 = 1 
? 3x + 7 – 7 = 1 – 7 (Subtracting 7) 
? 3x = – 6 
? x = – 2 
Required Answer = {-6, -3} 
Question 3. 
Solve 7 > 3x – 8; x ? N 
Solution: 
7 > 3x – 8 
=> 7 – 3x > 3x – 3x – 8 (Subtracting 3x) 
=> 7 – 7 – 3x > 3x – 3x – 8 – 7 (Subtracting 7) 
=> -3x > -15 
=> x < 5 (Dividing by -3) 
Required Answer = {1, 2, 3, 4} 
Note : Division by negative number reverses the inequality. 
Question 4. 
-17 < 9y – 8 ; y ? Z 
Solution: 
-17 < 9y – 8 
=> -17 + 8 < 9y – 8 + 8 (Adding 8) 
=> -9 < 9y 
=> -1 < y (Dividing by 9) 
Required number = {0, 1, 2, 3, 4, …} 
Question 5. 
Solve 9x – 7 = 28 + 4x; x ? W 
Solution: 
9x – 1 = 28 + 4x 
=> 9x – 4x – 7 = 28 + 4x – 4x (Subtracting 4x) 
=> 5x – 7 = 28 
=> 5x – 7 + 7 = 28 + 7 (Adding 7) 
=> 5x = 35 
=> x = 7 (Dividing by 5) 
Required answer = {0, 1, 2, 3, 4, 5, 6, 7} 
Question 6. 
Solve : x + 8 < 12 ; x ? W 
Solution: 
 
Question 7. 
Solve -5 (x + 4) > 30 ; x ? Z 
Solution: 
 
Question 8. 
Solve the inquation 8 – 2x > x – 5 ; x ? N. 
Solution: 
 
x = 1, 2, 3, 4 (x ? N) 
Solution set = {1, 2, 3, 4} 
Question 9. 
Solve the inequality 18 – 3 (2x – 5) > 12; x ? W. 
Solution: 
 
Question 10. 
Solve :  + 15 < 17; x ? W. 
Solution: 
 
Question 11. 
Solve : -3 + x < 2, x ? N 
Solution: 
 
Question 12. 
Solve : 4x – 5 > 10 – x, x ? {0, 1, 2, 3, 4, 5, 6, 7} 
Solution: 
 
Solution set = {4, 5, 6, 7} 
Question 13. 
Solve : 15 – 2(2x – 1) < 15, x ? Z. 
Solution: 
 
Question 14. 
Solve :  >  , x ? W. 
Solution: 
 
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