Question

can someone help me with this problem:
find an equation for the situation that you have 40 animals(cows and chickens) and 100 legs

Answer 1

do you know how many chickens and how many cows?

Answer 2

simple yes or no will do...

Answer 3

hello?

Answer 4

sorry! the total number or cows +chickens is 40 but i dont know how many of each

Answer 5

ok.... since we don't know, let's let:

x be the number of chickens, and
y be the number of cows...

BUT you do know this: x + y = 40, correct?

Answer 6

yes

Answer 7

now.. assuming these farm animals didn't come from Cherynoble, each chicken has 2 legs, and each cow has 4 legs.... correct?

Answer 8

yes so wouldnt that be 2x+4y=100?

Answer 9

good.... so you have the system of equations :

x + y = 40
2x + 4y = 100

do you know how to solve the system?

Answer 10

no thats the problem i dont know how to put the two equations together

Answer 11

there are a few ways to solve systems of equations.... of these two, which one do you know?

1 - substitution
2 - elimination

Answer 12

oh you mean like i make both equal to x and then put them together?

Answer 13

yes you can do that too.... :)

Answer 14

well what were you thinking about doing? can you help me with this part too. i dont want to mess it up

Answer 15

substituting.... the first equation into the second equation....

Answer 16

actually elimination would be faster...

Answer 17

ok how would i do that? i really dont remember... im sorry

Answer 18

i'll do substitution then....

Answer 19

i dont remember that either but whichever you like better

Answer 20

in the first equation, solve for y...
x + y = 40 ---> y = 40 - x

now let's replace the y in the second equation with this expression for y...

2x + 4y = 100
2x + 4(40 - x) = 100

by doing the substitution, we now have 1 equation with 1 variable.... can you solve for x now?

Answer 21

ya i think i can... thank you so much for all your help

Answer 22

yw...:)