# NCERT Solutions for Class 7 Maths

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# Simple Equations

Exercise 1

1.    Completer the last column of the table. 2.   Check whether the value given in the brackets is a solution to the given equation or not:

(a) n + 5 = 19(n = 1)               (b) 7n + 5 = 19 (n = -2)

(c) 7n + 5 = 19(n = 2)            (d) 4p – 3 = 13(p = 1)

(e) 4p – 3 = 13(p = -4)           (f) 4p – 3 = 13(p = 0)

3.   Solve the following equations by trial and error method:

(i) 5p + 2 = 17                         (ii) 3m – 14 = 4

4.    Write equations for the following statements:

(i) The sum of numbers x and 4 is 9.

(ii) 2 subtracted from y is 8.

(iii) Ten times a is 70.

(iv) The number b divided by 5 gives 6.

(v) Three-fourth of t is 15.

(vi) Seven times in plus 7 gets you 77.

(vii) One-fourth of a number x minus 4 gives 4.

(viii) If you take away 6 from 6 times y, you get 60.

(ix) If you add 3 to one-third of z, you get 30.

5.    Write the following equations in statement form: 6.    Set up an equation in the following cases:

(i) Irfan says that he has 7 marbles more than five times the marbles Parmit has. Irfan has 37 marbles. (Tale m to be the number of Parmit’s marbles.)

(ii) Laxmi’s father is 49 years old. He is 4 years older than three times Laxmi’s age. (Take Laxmi’s age to be y years.)

(iii) The teacher tells the class that the highest marks obtained by a student in her class are twice the lowest marks plus 7. The highest score is 87. (Take the lowest score to be)

(iv) In an isosceles triangle, the vertex angle is twice either base angle. (Let the base angle be b in degrees. Remember that the sum of angles of a triangle is 180°.)

Exercise 2

7.    Give first the step you will use to separate the variable and then solve the equations:

(a) x – 1 = 0      (b) x + 1 = 0      (c) x – 1 = 5

(d) x + 6 = 2    (e) y – 4 = -7      (f) y – 4 = 4

(g) y + 4 = 4     (h) y + 4 = -4

8.   Give first the step you will use to separate the variable and then solve the equations 9.   Give first the step you will use to separate the variable and then solve the equations 10.  Solve the following equation: Exercise 3

11.  Solve the following equations: 12.  Solve the following equations:

(a) 2 (x + 4) = 12        (b) 3 (n – 5) = 21

(c) 3 (n – 5) = -21        (d) 3 – 2(2 – y) = 7

(e) -4 (2 – x) = 9          (f) 4(2 – x) = 9

(g) 4 + 5(p – 1) = 34    (h) 34 – 5(p – 1) = 4

13.  Solve the following equations:

(a) 4 = 5(p – 2)                (b) -4 = 5(p – 2)

(c) -16 = -5(2 – p)            (d) 10 = 4 + 3(t + 2)

(e) 28 = 4 +3 (t +5)        (f) 0 = 16 + 4(m – 6)

14.  (a) Construct 3 equations starting with x = 2.

(b) Construct 3 equations starting with x = -2.

Exercise 4

15.  Set up equations and solve them to find the unknown numbers in the following cases:

(a) Add 4 to eight times a number; you get 60.

(b) One-fifth of a number minus 4 gives 3.

(c) If I take three-fourth of a number and add 3 to it, I get 21.

(d) When I subtracted 11 from twice a number, the result was 15.

(e) Munna subtracts thrice the number of notebooks he has from 50, he finds the result to be 8.

(f) Ibenhal thinks of a number. If she adds 19 to it divides the sum by 5, she will get 8.

(g) Answer thinks of a number. If he takes away 7 from of the number, the result is 16.  Solve the following:

(a) The teacher tells the class that the highest marks obtained by a student in her class are twice the lowest marks plus 7. The highest score is 87. What is the lowest score?

(b) In an isosceles triangle, the base angles are equal. The vertex angle is 40°. What are the base angles of the triangle? (Remember, the sum of three angles of a triangle is 180°.)

(c) Sachin scored twice as many runs as Rahul. Together, their runs fell two short of a double century. How many runs did each one score?

17.  Solve the following:

(a) Irfan says that he has 7 marbles more than five times the marbles Parmit has. Irfan has 37 marbles. How many marbles does Parmit have?

(b) Laxmi’s father is 49 years old. He is 4 years older than three times Laxmi’s age. What is Laxmi’s age?

(c) People of Sundergram planted a total of 102 trees in the village garden. Some of the trees were fruit trees. The number of non-fruit trees were two more than three times the number of fruit trees. What was the number of fruit trees planted?

18.  Solve the following riddle:

I am a number, Tell my identity!

Take me seven times over, And add a fifty!

To reach a triple century, You still need forty!

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