Question

18 animals in a pet store. some are birds and some are dogs. there are 50 legs in all. how many birds and how many dogs are there

Answer 1

Answer:

7 dogs and 11 birds

Step-by-step explanation:

18 animals in a pet store. some are birds and some are dogs. there are 50 legs in all.

We know that birds has 2 legs and dogs has 4 legs

Let 'b' be the number of birds

and 'd' be the number of dogs

Total animals = 18

$b+d= 18$

there are 50 legs in all. total legs = 50

$2b+4d= 50$

WE got two equations, now we solve for 'd'

Multiply the first equation by -2 to cancel out 'b'

$b+d= 18$

$-2b-2d= -36$

$2b+4d= 50$

--------------------------------------

            $2d= 14$

Divide both sides by 2

d= 7

The number of dogs=7

$b+d= 18$

$b+7= 18$

Subtract 7 from both sides

b=11

The number of birds = 11

Answer 2

A bird has only 2 legs, and a dog has 4 legs.
x=number of birds
y=number of dogs

We can susggest this system of equations:

x+y=18
2x+4y=50

We can solve this system of equations by substitution method.
x+y=18        ⇒      y=18-x

2x+4(18-x)=50
2x+72-4x=50
-2x=50-72
-2x=-22
x=-22/-2
x=11

y=18-x
y=18-11
y=7

Answer: we have 11 birds and 7 dogs.