What is 3 4 5 8

Calculate fractions

Leonie needs a new bike. At the dealer she saw a used cross bike that costs $ 160 $. Her father says that if Leonie can collect $ 3/4 $ of the money himself, he'll add the rest. Now Leonie is wondering how much money she has to save herself.

So you determine the fraction $$ 3/4 $$ of the $$ 160 $$ €. The $$ 160 $$ € are the whole.



Divide the whole thing into 4 parts. You determine $$ 1/4 $$.



Mathematically: Divide $$ 160 $$ € by the denominator.
$$160$$ € $$:$$ $$4 = 40$$ €.

Take 3 parts. You determine $$ 3/4 $$.



Mathematically: $$ 40 $$ € $$ * $$ $$ 3 = 120 $$ €

So Leonie has to save $ 120 $. Then she gets the rest of it.


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The calculation method

So the fraction ($$ 3/4 $$) tells you how to do the math:

  1. Divide the whole thing.
    $$160$$ € $$:$$ $$= 40 $$ €

  2. You take the result with you.
    $$40$$ € $$* $$ $$= 120$$ €

How to calculate the fraction:

  1. Divide the whole thing.
  2. Multiply the result by.

That's how it works!

In some cases it is easier to reverse the two steps, so

  1. Take the whole thing with you.
  2. Divide the result by.

Example:
Philipp likes to eat fish fingers. However, he has found that his father burns about $$ 2/6 $$ fish fingers in a pack of $$ 15 $$ pieces.

$$ 15 $$ (the whole) cannot be easily divided by. But if you take $$ 15 $$ with you first, you will get $$ 30 $$.

$$15$$ $$*$$ = $$30$$

Now sharing is easier.

$$30 :$$ $$= 5$$

So many fish fingers burned! Poor Philip!

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Shorten, shorten

Take a close look at the fraction first: if you can shorten it, always do it. Then you can calculate with smaller numbers.

In the case of Philip's fish finger fiasco, it would have looked like this:

$$2/6 = (2:2)/(6:2) = 1/3$$

Here the counter is even $$ 1 $$. Then you just have to divide the whole thing through, because you don't have to take it with me anymore.

$$15$$ $$ :$$ $$= 5$$

So you get the same result.

Don't forget: smaller numbers make arithmetic easier! :)