Page 114 - Start Up Mathematics_7

Solution: (a) Let Rohit have n marbles. (b) Let the lowest marks be l.

Imran has 29 marbles. Highest score = 85
∴ 4n – 3 = 29 ∴ 3l – 2 = 85

(c) Let Garima’s age be y years. (d) Let one of the angles be a.
Garima’s father’s age = 43 years ∴ The other angle = 2a

∴ 2y + 19 = 43 By angle sum property of triangle,
⇒ a + 2a + 90 = 180
⇒ 3a = 90°

EXERCISE 7.1

1. Complete the following table:

Whether the equation
S. No. Equation Value
is satisfied (Yes/No)
(i) x – 5 = 0 x = 0

(ii) x + 7 = 2 x = –5

(iii) 3x – 24 = 0 x = 6

(iv) 16x + 16 = 0 x = –1

2. Check whether the value given in the brackets is the solution of the corresponding equation
or not:
(a) x + 13 = 6 (x = –7) (b) 8x – 4 = 28 (x = 4) (c) 3p – 4 = 14 (p = 5)
3. Write equations for the following statements:

(a) The sum of nine times a and 6 is 24.
(b) A number b divided by 7 gives 5.

(c) If 12 is taken away from five times y, you get 40.
(d) Simran’s father is 41 years old. He is 5 years older than three times Simran’s age.
(e) In an isosceles triangle, the base angles are equal. Each of the base angle is double the
vertex angle.

(f) The sum of two consecutive odd numbers is 44.
4. Write the following equations in statement form:

3p
(a) x + 7 = 9 (b) = 16 (c) 4p + 2 = 20 (d) 2x – 5 = 20
p + 5

Trial and Error Method

An equation can be solved by trial and error method by substituting different values of the variable
till the equation is satisfied. Although this method is based on the definition, yet it is not convenient
to obtain the solution.

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