Wykonajmy obliczenia.

a)

$25+75=25+5+70=30+70=100$

$80-44=80-40-4=40-4=36$

$100-76=100-70-6=30-6=24$

$8\cdot 7\underline{0}=56\underline{0}$

$304:2=300:2+4:2=150+2=152$

$32:8=4$

$250:2=125$

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b)

$560+330=890$

$100-650=1000-600-50=400-50=350$

$10\cdot 97=970$

$31\cdot 2\underline{0}=62\underline{0}$

$150\cancel{0}:3\cancel{0}=50$

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c)

$3500+4500=3500+500+4000=4000+4000=8000$

$10000-7500=10000-7000-500=3000-500=2500$

$6600-4500=6600-4000-500=2600-500=2100$

$30\cdot 3\underline{00}=90\underline{00}$

$36\underline{0}\cancel{0}:4\cancel{0}=9\underline{0}$