Maths CBSE Class 7 - Simple Equations

Simple Equations

Ø  An equation is a condition on a variable such that two expressions in the variable should have equal value. At least one of the expressions must contain a variable.

Ø  In an equation there is always an equal sign.

Ø  The value of the variable for which the equation is satisfied is called the solution (root) of the equation.

Ø  An equation remains the same if the LHS and RHS are interchanged.

Ø  Transposing means moving to the other side.

Ø  Transposition of a number has the same effect as adding same number to(or subtracting the same number from) both sides of the equation.

Ø  When we transpose a number from one side to other side of the equation, its sign is changed.

Ø  In case of the balanced equation, if we

(i)   Add the same number to both sides, or

(ii)   Subtract the same number from both the sides, or

(iii)   Multiply both sides by the same number, or

(iv)   Divide both sides by the same number, the balance remains undisturbed, ie the value of the LHS remains equal to the value of the RHS.

Examples of equation

2x+3=6,     y+1=7,   P - 3=10

Question

(1)   Write the following statements in equation form

(a)    The sum of numbers m and 16 is 60

Answer:  m+16=60

(b)   One fourth of  number y minus 7 is 12

Answer:  y/4 – 7=12

(2)   Write the following equation in statement form

(i)                 2m/3 =9

           Answer: Two-Third of m is 9

(ii)               n/2 + 5 = 10

    Answer: Add 5 to half of a number is 10