The workings.
There are 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?
Say we set dog as x and bird as y. From the question we get:
x + y = 18 (Eq. 1)
4x + 2y = 50 (Eq. 2)
Use these to find the value of x and y.
From Eq. 1 we get : x = 18 – y
Insert this into Eq. 2 : 4(18-y) + 2y = 50
Calculating that, we get :
72 – 4y + 2y = 50
2y = 22
y = 11
So, we have 11 birds. Let’s use this value into Eq. 1, and we get:
x + 11 = 18
x = 7
So, we have 7 dogs.
Sorted!
