Math Is Fun Forum

angelboy

Member

Registered: 2009-04-13

Posts: 2

basic algebra -help!

This a primary question I cannot work out... any takers?

Problem: Animals.

Old Mac Donald has 10 animals. The ten animals are either ducks or sheep and in total the 10 animals have 32 legs. How many ducks and how many sheep does the farmer have?

c) Solve the problem using Algebra as an upper middle school student may do it.
          Hint: Let the number of sheep be n
                   Number of ducks = (in terms of n)
                   Now make and solve an equation for the number of legs.

         Show all the steps in your solutions and comment on the process  and the strategies you use.

Last edited by angelboy (2009-04-13 11:32:11)

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: basic algebra -help!

Old MacDonald has 10 animals in all, and they are all ducks or sheep.
So [ducks] + [sheep] = 10, which means [ducks] = 10 - [sheep].

So using the definition of n, he has n sheep and (10-n) ducks.

You can then say that the number of legs his animals have is 4n + 2(10-n).
You know that this is 32, so now you've got an equation that you can solve.

---

Why did the vector cross the road?
It wanted to be normal.

smiyc86

Member

Registered: 2009-03-19

Posts: 78

Re: basic algebra -help!

how can u assume that no legs of any animal are broken

---

I love Maths and Music ... dunno which more