a)
\(125+356+275+1244\)
\(=481+275+1244\)
\(=756+1244\)
\(=2000\)
b)
\(2+7+12+17+22+27+32+37+42+47\)
\(=9+12+17+22+27+32+37+42+47\)
\(=21+17+22+27+32+37+42+47\)
\(=38+22+27+32+37+42+47\)
\(=60+27+32+37+42+47\)
\(=87+32+37+42+47\)
\(=119+37+42+47\)
\(=156+42+47\)
\(=198+47\)
\(=245\)
c)
\((274+2935)+2065+426\)
\(=3209+2065+426\)
\(=5274+426\)
\(=5700\)
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a. 125+356+275+1244
=(125+275)+(356+1244)
=400+1600
=2000
c. (274+2935)+2065+426
=274+2935+2065+426
=(274+426)+(2935+2065)
=700+5000
=5700
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