My post was in a little more detail than what I actually was taught. Basically, the teacher wrote down two equal fractions next to each other. He then drew arrows from one part to the other to show the pattern. So if A was unknown, he'd draw an arrow from B to C and say, "multiply these together," then he'd draw an arrow from C to D and say "Divide the result by this."
You can see the pattern of multiplying the crosswise numbers which don't contain the unknown, then dividing by the third to find the answer.
My post above is more the algebraic equivalent of what he taught. Even though I did get some very basic algebra back then, I didn't get anything quite that complex until about the 7th grade.
It was a little thing he taught really to help us understand a little better when he started teaching us about ratios. For example, Fred spent 18c of every quarter he had. If he spent $10.80, how much money did he have originally? This could be represented by the ratios .18:.25 = 10.80:x
X can be calculated using the same idea as with fractions.
(.25*10.80)/.18
BTW, how can you go eight years without fractions? I can't imagine all you did was add, subtract, multiply, and divide whole numbers all that time. They must've taught you something useful.
Or do you learn decimals first? Over here we learn fractions, then move to decimals as an advanced topic (or at least we did when I was in school). It's easier to grasp that when a pie is cut into eight pieces and you take three pieces, then you have 3/8th of the pie, rather than you have 0.375 of the pie.
You can see the pattern of multiplying the crosswise numbers which don't contain the unknown, then dividing by the third to find the answer.
My post above is more the algebraic equivalent of what he taught. Even though I did get some very basic algebra back then, I didn't get anything quite that complex until about the 7th grade.
It was a little thing he taught really to help us understand a little better when he started teaching us about ratios. For example, Fred spent 18c of every quarter he had. If he spent $10.80, how much money did he have originally? This could be represented by the ratios .18:.25 = 10.80:x
X can be calculated using the same idea as with fractions.
(.25*10.80)/.18
BTW, how can you go eight years without fractions? I can't imagine all you did was add, subtract, multiply, and divide whole numbers all that time. They must've taught you something useful.
Or do you learn decimals first? Over here we learn fractions, then move to decimals as an advanced topic (or at least we did when I was in school). It's easier to grasp that when a pie is cut into eight pieces and you take three pieces, then you have 3/8th of the pie, rather than you have 0.375 of the pie.