Mental Maths Questions and Answers: Simple Equations | Mental Math for Class 7 PDF Download

 Page 1


 
  
 
  
SIMPLE EQUATIONS 
 Points to remember: 
? The collection of whole numbers and negative numbers is called 
integers. 
? An equation is a statement of equality which contains a variable on 
one or on both the sides of the equation. 
? An equation involving only a linear polynomial is called a linear equation. 
For example: 3x + 12 = 90 etc. 
? An equation remains the same if the LHS and the RHS are interchanged. 
? Taking terms of one side to other side is called transposing. When we 
transpose a number from one side of the equation to the other side, we 
change its sign example 12 p – 11 = 25  ? 12 p = 25 + 11. 
? An equation does not change, if  
? Same quantity is added to both sides 
? Same quantity is subtracted from both sides 
? Both sides are multiplied by same non zero quantity. 
? Both sides are divided by same non zero quantity. 
 
Questions: 
1. 2x – 14 = 10 
2. 3x + 21 = 0  
3. 2x – 9 = -3  
4. 5x – 12 = 18  
5. -3x – 1 = 1 – 2x 
6. 8x = 20 + 3x 
Page 2


 
  
 
  
SIMPLE EQUATIONS 
 Points to remember: 
? The collection of whole numbers and negative numbers is called 
integers. 
? An equation is a statement of equality which contains a variable on 
one or on both the sides of the equation. 
? An equation involving only a linear polynomial is called a linear equation. 
For example: 3x + 12 = 90 etc. 
? An equation remains the same if the LHS and the RHS are interchanged. 
? Taking terms of one side to other side is called transposing. When we 
transpose a number from one side of the equation to the other side, we 
change its sign example 12 p – 11 = 25  ? 12 p = 25 + 11. 
? An equation does not change, if  
? Same quantity is added to both sides 
? Same quantity is subtracted from both sides 
? Both sides are multiplied by same non zero quantity. 
? Both sides are divided by same non zero quantity. 
 
Questions: 
1. 2x – 14 = 10 
2. 3x + 21 = 0  
3. 2x – 9 = -3  
4. 5x – 12 = 18  
5. -3x – 1 = 1 – 2x 
6. 8x = 20 + 3x 
 
  
 
7. x - 
?? ?? = 1 
?? ?? 
8. 
?? ?? 
 y + 
?? ?? y = y – 7  
9. 5(t – 2) + 3(t + 1) = 25  
10. 6y = 
?? ?? (2y – 7)  
11. 
?? ?? (2y – 1) = 3y – 5  
12.  
?? ?? +?? ?? = 3y – 8  
13. 
?? -?? ?? – 2 = -??  
14. 
?? ?? ?? + 
?? ?? = 
????
??????
  
15. 
?? ?? -?? ?? ?? = 2  
16. 
???? +?? ???? +?? = 
?? ?? , z? - 
?? ??  
17. p – 2 =
?? ?? (3p – 1)  
18. 
???? -?? ?? = 9  
19. 3p – 0.7 = 1.4  
20. 4p + 0.8 = 7.2  
21. 
?? ?? ?? -????
 = 9  
22. 1.8 q = 24 + q  
23. 0.1 (3q – 1) = 0.2 (1 – 2q)  
24. 
???? -?? ???? +?? = 5 , p ?  -
?? ??  
25. 
?? -?? ?? -????
 = 2 , q ? ½  
26.  
?? -?? ???? +?? = 1 , k? - 1/6  
Page 3


 
  
 
  
SIMPLE EQUATIONS 
 Points to remember: 
? The collection of whole numbers and negative numbers is called 
integers. 
? An equation is a statement of equality which contains a variable on 
one or on both the sides of the equation. 
? An equation involving only a linear polynomial is called a linear equation. 
For example: 3x + 12 = 90 etc. 
? An equation remains the same if the LHS and the RHS are interchanged. 
? Taking terms of one side to other side is called transposing. When we 
transpose a number from one side of the equation to the other side, we 
change its sign example 12 p – 11 = 25  ? 12 p = 25 + 11. 
? An equation does not change, if  
? Same quantity is added to both sides 
? Same quantity is subtracted from both sides 
? Both sides are multiplied by same non zero quantity. 
? Both sides are divided by same non zero quantity. 
 
Questions: 
1. 2x – 14 = 10 
2. 3x + 21 = 0  
3. 2x – 9 = -3  
4. 5x – 12 = 18  
5. -3x – 1 = 1 – 2x 
6. 8x = 20 + 3x 
 
  
 
7. x - 
?? ?? = 1 
?? ?? 
8. 
?? ?? 
 y + 
?? ?? y = y – 7  
9. 5(t – 2) + 3(t + 1) = 25  
10. 6y = 
?? ?? (2y – 7)  
11. 
?? ?? (2y – 1) = 3y – 5  
12.  
?? ?? +?? ?? = 3y – 8  
13. 
?? -?? ?? – 2 = -??  
14. 
?? ?? ?? + 
?? ?? = 
????
??????
  
15. 
?? ?? -?? ?? ?? = 2  
16. 
???? +?? ???? +?? = 
?? ?? , z? - 
?? ??  
17. p – 2 =
?? ?? (3p – 1)  
18. 
???? -?? ?? = 9  
19. 3p – 0.7 = 1.4  
20. 4p + 0.8 = 7.2  
21. 
?? ?? ?? -????
 = 9  
22. 1.8 q = 24 + q  
23. 0.1 (3q – 1) = 0.2 (1 – 2q)  
24. 
???? -?? ???? +?? = 5 , p ?  -
?? ??  
25. 
?? -?? ?? -????
 = 2 , q ? ½  
26.  
?? -?? ???? +?? = 1 , k? - 1/6  
 
  
 
27. 
???? 
???? -?? = - 1 , k ? 1  
28. 2t – 1 =  
?? ?? (5 – 2 t)  
29. 0.9 (1 – p) = 0.1 p – 3  
30. 0.3 x + 0.4 = 0.28 x + 1.16  
31. The length of a rectangle is 5m more than its breadth and its 
perimeter is 230m. Find its length and breadth.  
32. A number when added to its one third gives result 16. Find the 
number.  
33. When the smaller of two consecutive integers is added to three times 
the larger integer the result is 83. Find both the integers.  
34. After 10 years Monika will be three times as old as she was four years 
ago. What is her present age?  
35. If 5 is subtracted from three times a number, the result is 16. Find 
the number.  
36. The sum of three consecutive even numbers is 42. Find these 
numbers.  
37. Naina thoughts of a number. She multiplied it by 2 added 5 to the 
product then obtained 17 as result. What is the number she had 
thought of?  
38. Two adjacent sides of a square are given in fig below. Find the 
measurement of sides of the square. 
 
Page 4


 
  
 
  
SIMPLE EQUATIONS 
 Points to remember: 
? The collection of whole numbers and negative numbers is called 
integers. 
? An equation is a statement of equality which contains a variable on 
one or on both the sides of the equation. 
? An equation involving only a linear polynomial is called a linear equation. 
For example: 3x + 12 = 90 etc. 
? An equation remains the same if the LHS and the RHS are interchanged. 
? Taking terms of one side to other side is called transposing. When we 
transpose a number from one side of the equation to the other side, we 
change its sign example 12 p – 11 = 25  ? 12 p = 25 + 11. 
? An equation does not change, if  
? Same quantity is added to both sides 
? Same quantity is subtracted from both sides 
? Both sides are multiplied by same non zero quantity. 
? Both sides are divided by same non zero quantity. 
 
Questions: 
1. 2x – 14 = 10 
2. 3x + 21 = 0  
3. 2x – 9 = -3  
4. 5x – 12 = 18  
5. -3x – 1 = 1 – 2x 
6. 8x = 20 + 3x 
 
  
 
7. x - 
?? ?? = 1 
?? ?? 
8. 
?? ?? 
 y + 
?? ?? y = y – 7  
9. 5(t – 2) + 3(t + 1) = 25  
10. 6y = 
?? ?? (2y – 7)  
11. 
?? ?? (2y – 1) = 3y – 5  
12.  
?? ?? +?? ?? = 3y – 8  
13. 
?? -?? ?? – 2 = -??  
14. 
?? ?? ?? + 
?? ?? = 
????
??????
  
15. 
?? ?? -?? ?? ?? = 2  
16. 
???? +?? ???? +?? = 
?? ?? , z? - 
?? ??  
17. p – 2 =
?? ?? (3p – 1)  
18. 
???? -?? ?? = 9  
19. 3p – 0.7 = 1.4  
20. 4p + 0.8 = 7.2  
21. 
?? ?? ?? -????
 = 9  
22. 1.8 q = 24 + q  
23. 0.1 (3q – 1) = 0.2 (1 – 2q)  
24. 
???? -?? ???? +?? = 5 , p ?  -
?? ??  
25. 
?? -?? ?? -????
 = 2 , q ? ½  
26.  
?? -?? ???? +?? = 1 , k? - 1/6  
 
  
 
27. 
???? 
???? -?? = - 1 , k ? 1  
28. 2t – 1 =  
?? ?? (5 – 2 t)  
29. 0.9 (1 – p) = 0.1 p – 3  
30. 0.3 x + 0.4 = 0.28 x + 1.16  
31. The length of a rectangle is 5m more than its breadth and its 
perimeter is 230m. Find its length and breadth.  
32. A number when added to its one third gives result 16. Find the 
number.  
33. When the smaller of two consecutive integers is added to three times 
the larger integer the result is 83. Find both the integers.  
34. After 10 years Monika will be three times as old as she was four years 
ago. What is her present age?  
35. If 5 is subtracted from three times a number, the result is 16. Find 
the number.  
36. The sum of three consecutive even numbers is 42. Find these 
numbers.  
37. Naina thoughts of a number. She multiplied it by 2 added 5 to the 
product then obtained 17 as result. What is the number she had 
thought of?  
38. Two adjacent sides of a square are given in fig below. Find the 
measurement of sides of the square. 
 
 
  
 
39. The difference between two numbers is 7. Six times the smaller plus the 
larger is 77. Find the numbers. 
40. The sum of two numbers is 25. One of the numbers exceeds the other by 9. 
Find the numbers.  
41. The sum of ages of father and his son is 75 years. If the age of the son is 25 
years, find the age of father. 
42. Find three consecutive whole numbers whose sum is 84. 
43. In a hostel mess 50 kg of rice is consumed per day. If each student gets 400 
gram of rice per day, find the number of students in the hostel mess. 
44. Manogya is 3 years younger than her brother Shubh. If sum of their ages 
be 25 years, find their present ages. 
45. The ages of Kishan and Rishabh are in the ratio of 4 : 5. Ten years hence 
the ratio of their ages will be 6 : 7. Find their present ages. 
46. Find the measure of an angle if its supplement measures 39° more than 
twice its complement. 
47. In ? ABC if ?A = (3x)° , ?B = (2x + 60) ° and ?C = (5x – 40)° . Find these 
angles. 
48. Each of the two equal sides of an isosceles triangle is twice as large as the 
third side. If the perimeter of the triangle is 30 cm. find the length of each 
side of the triangle. 
49. In a bag, the number of one rupee coins is three times the number of two 
rupees coins. If the total worth of the coins is ` 120. Find the number of 
two rupees coins. 
50. The interest received by Manas is ` 30 more than that of Kishan. If the 
total interest received by them is `120, find the interest received by Manas. 
  
Page 5


 
  
 
  
SIMPLE EQUATIONS 
 Points to remember: 
? The collection of whole numbers and negative numbers is called 
integers. 
? An equation is a statement of equality which contains a variable on 
one or on both the sides of the equation. 
? An equation involving only a linear polynomial is called a linear equation. 
For example: 3x + 12 = 90 etc. 
? An equation remains the same if the LHS and the RHS are interchanged. 
? Taking terms of one side to other side is called transposing. When we 
transpose a number from one side of the equation to the other side, we 
change its sign example 12 p – 11 = 25  ? 12 p = 25 + 11. 
? An equation does not change, if  
? Same quantity is added to both sides 
? Same quantity is subtracted from both sides 
? Both sides are multiplied by same non zero quantity. 
? Both sides are divided by same non zero quantity. 
 
Questions: 
1. 2x – 14 = 10 
2. 3x + 21 = 0  
3. 2x – 9 = -3  
4. 5x – 12 = 18  
5. -3x – 1 = 1 – 2x 
6. 8x = 20 + 3x 
 
  
 
7. x - 
?? ?? = 1 
?? ?? 
8. 
?? ?? 
 y + 
?? ?? y = y – 7  
9. 5(t – 2) + 3(t + 1) = 25  
10. 6y = 
?? ?? (2y – 7)  
11. 
?? ?? (2y – 1) = 3y – 5  
12.  
?? ?? +?? ?? = 3y – 8  
13. 
?? -?? ?? – 2 = -??  
14. 
?? ?? ?? + 
?? ?? = 
????
??????
  
15. 
?? ?? -?? ?? ?? = 2  
16. 
???? +?? ???? +?? = 
?? ?? , z? - 
?? ??  
17. p – 2 =
?? ?? (3p – 1)  
18. 
???? -?? ?? = 9  
19. 3p – 0.7 = 1.4  
20. 4p + 0.8 = 7.2  
21. 
?? ?? ?? -????
 = 9  
22. 1.8 q = 24 + q  
23. 0.1 (3q – 1) = 0.2 (1 – 2q)  
24. 
???? -?? ???? +?? = 5 , p ?  -
?? ??  
25. 
?? -?? ?? -????
 = 2 , q ? ½  
26.  
?? -?? ???? +?? = 1 , k? - 1/6  
 
  
 
27. 
???? 
???? -?? = - 1 , k ? 1  
28. 2t – 1 =  
?? ?? (5 – 2 t)  
29. 0.9 (1 – p) = 0.1 p – 3  
30. 0.3 x + 0.4 = 0.28 x + 1.16  
31. The length of a rectangle is 5m more than its breadth and its 
perimeter is 230m. Find its length and breadth.  
32. A number when added to its one third gives result 16. Find the 
number.  
33. When the smaller of two consecutive integers is added to three times 
the larger integer the result is 83. Find both the integers.  
34. After 10 years Monika will be three times as old as she was four years 
ago. What is her present age?  
35. If 5 is subtracted from three times a number, the result is 16. Find 
the number.  
36. The sum of three consecutive even numbers is 42. Find these 
numbers.  
37. Naina thoughts of a number. She multiplied it by 2 added 5 to the 
product then obtained 17 as result. What is the number she had 
thought of?  
38. Two adjacent sides of a square are given in fig below. Find the 
measurement of sides of the square. 
 
 
  
 
39. The difference between two numbers is 7. Six times the smaller plus the 
larger is 77. Find the numbers. 
40. The sum of two numbers is 25. One of the numbers exceeds the other by 9. 
Find the numbers.  
41. The sum of ages of father and his son is 75 years. If the age of the son is 25 
years, find the age of father. 
42. Find three consecutive whole numbers whose sum is 84. 
43. In a hostel mess 50 kg of rice is consumed per day. If each student gets 400 
gram of rice per day, find the number of students in the hostel mess. 
44. Manogya is 3 years younger than her brother Shubh. If sum of their ages 
be 25 years, find their present ages. 
45. The ages of Kishan and Rishabh are in the ratio of 4 : 5. Ten years hence 
the ratio of their ages will be 6 : 7. Find their present ages. 
46. Find the measure of an angle if its supplement measures 39° more than 
twice its complement. 
47. In ? ABC if ?A = (3x)° , ?B = (2x + 60) ° and ?C = (5x – 40)° . Find these 
angles. 
48. Each of the two equal sides of an isosceles triangle is twice as large as the 
third side. If the perimeter of the triangle is 30 cm. find the length of each 
side of the triangle. 
49. In a bag, the number of one rupee coins is three times the number of two 
rupees coins. If the total worth of the coins is ` 120. Find the number of 
two rupees coins. 
50. The interest received by Manas is ` 30 more than that of Kishan. If the 
total interest received by them is `120, find the interest received by Manas. 
  
 
  
 
Answer: 
Q. NO. ANSWER  Q. NO. ANSWER  
1.  ?? = ????  26.  ?? = -?? /??  
2.  ?? = -??  27. 
?? =
?? ??  
3.  ?? = ??  28. ?? = ??  
4. ?? = ??  29. ?? = ?? . ??  
5. ?? = -??  30. ?? = ????  
6. ?? = ??  31. l = ???? m,  b= ???? m 
7.  ?? = ??  32. 
12 
8. ?? = ????  33. 
20, 21 
9. ?? = ??  34. 
11 years 
10. ?? = -??  35. 
7 
11.  ?? = -????  36. 
12, 14, 16  
12. 
?? =
????
??  
37. 
6 
13. ?? = ??  38. 
16 cm 
14. ?? = ??  39. 
10, 17 
15. 
?? =
?? ??  
40. 
8, 17 
16. ?? = -??  41. 
50 years 
17. 
?? =
?? ??  
42. 
27, 28, 29 
18. ?? = ????  43. 
125 
19. ?? = ?? . ??  44. 
11, 14 years 
20. ?? = ?? . ??  45. 
20 and 25 years 
21. 
?? =
?? ??  
46. 
???? °  
22. ?? = ????  47. ??? = ???? °, ??? =
???? °, ??? = ???? °  
23. ?? = ?? /??  48. 12 cm, 12 cm, 6 cm 
24. ?? = -??  49 24 
25. ?? = ??  50. `75