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

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.

Answer 2

7 dogs and 11 birds

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