(i) 10 students of Class X took part in Mathematics quiz. If the number of girls is 4 more than the number of boys, find the number of boys and girls who took part in the quiz.
(i) Let the number of boys be x and number of girls be y.
Case I. x + y = 10 ...(i)
Case II. y = x + 4
⇒ x - y = -4 ...(ii)
We have, x + y = 10
⇒ x = 10 - y
Thus, we have following table :
Fig. 3.4.
We have, x - y = -4
⇒ x = y - 4
Thus we have following table :
When we plot the graph of the given equation, we find that both the lines intersect at me point (3, 7). So.r = 3,y = 7 is the required solution of the pair of linear equation.
Hence, the number of boys be 3 and the number of girls be 7, who took part in quiz.
Aftab tells his daughter, 'Seven years ago, I was seven times as old as you were then. Also, three years from now, I shall be three times as old as you will be'. (Isn’t this interesting?) Represent this situation algebraically and graphically.
