How do i calculate 200 x 25 + 5x 800 5 x 20 +

Thank you very much for the detailed answer, i will try to mimik it and memorize the technique into action.

Update: It worked as a charm with your advice, thank you.

How do i calculate 200 x 25 + 5x 800
                               5 x 20 + 25 x 4 

$\frac {200\times 2\; + \;5\times 800}{ 5 \times 20 \;+\; 25 \times 4 }\\ =\frac {200\times 2\; + \;5\times 800}{ 5 \times 20 \;+\; 25 \times 4 }\\ \qquad 200*2=2*2\;and\; add\; the\; two\; zeros = 400\\ \qquad 5*800=5*8\;and\; add\; the\; two\; zeros = 4000\\ \qquad 5*20=100\\ \qquad 25*4=100\\ \qquad \mbox{Put it all together and you get...}\\~\\ =\frac {400\; + \;4000}{ 100 \;+\; 100 }\\ =\frac {4400}{ 200 }\\ =\frac {4400\div 100}{ 200\div 100 }\\ =\frac {44}{ 2 }\\ =\frac {44\div 2}{ 2 \div 2}\\ =\frac {22}{ 1 }\\ =22$

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