Question

In a deer park the number of heads and the number of legs of deer and visitors were counted and it was found that there were 39 heads and 132 legs. Find the number of deers and visitors in the park, using graphical method.

Answer 1

let deer be represented by d and visitors represented by v.
deer and visitors have one head each, so d + v = 39
a deer has 4 legs and a visitor has 2 legs, so 4d + 2v = 132

d + v = 39
4d + 2v = 132

d = 39 - v

4(39 - v) + 2v = 132
156 - 4v +2v = 132
-2v = 132 - 156
-2v = -24
v = -24/-2
v = 12

d = 39 - v
d = 39 - 12
d = 27

there are 12 visitors and 27 deer.

to check: 
d + v = 39
27 + 12 = 39
39 = 39

4d + 2v = 132
4(27) + 2(12) = 132
108 + 24 = 132
132 = 132

Answer 2

Let No.of visitors be x No.of deer's be y No.of heads = x+ y=39 No.of legs =2x+4y=132 Since visitor has two legs and deer have four. Plotting these lines on a graph gives you a point of intersection which tells the answer You can also find it by solving the above two equations. Which is x+y=39=>x=39-y Substitute in second equation 2x+4y=132=>x+2y=66 39-y+2y=66 Y=66-39=27 X=39-y=39-27=12 There fore the required answer is there are 12 visitors and 27 deer