pop quiz.

if i buy 10kg of rice, i'm short $3. if i buy 5kg, i've got $1 extra. how much does a kilo of rice cost?

what i want to know is whether you can solve this without using simultaneous equations. thing is that is a pri 3 standard question and i'm quite sure simultaneous equations'd be beyond a 9 year old's comprehension. so does anyone have an easier method then?


i'm sure there is one. a dead obvious one. one that'll make me smack myself in the forehead and go "doh!".

but that's what 12 years of math does to you.