how do i easily figure out stuff like 3,2/0.04
Well... I'm not too great at calculations in my head, but here's one way.
The question is... how many times does 0.04 go into 3.2 ?
4  goes into  32  8  times,  so... 
0.4  goes into  32  80  times, 

0.04  goes into  32  800  times,  and 
0.04  goes into  3.2  80  times. 

Here's a suggestion if the fractions combined with decimals are messing with your mind.
\(\frac{3.2}{0.04}*\frac{100}{100}=\frac{320}{4}\)
Multiplying by 100/100 has no effect on the value of this fraction as it is equivalent of multiplying by 1.
\(\frac{320}{4}=\frac{32*10}{4}=\frac{8*10}{1}=80\)
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