用简便方法计算.6.2+5.18+2.8 15

用简便方法计算.6.2+5.18+2.8 15.35-(5.35+7.2) 3.63-1.25+17.37-8.75 13.7-9.9 98×45+2×45 56×102.

(1)6.2+5.18+2.8,
=6.2+2.8+5.18,
=9+5.18,
=14.18;

(2)15.35-(5.35+7.2),
=15.35-5.34-7.2,
=10-7.2,
=2.8;

(3)3.63-1.25+17.37-8.75,
=(3.63+17.37)-(1.25+8.75),
=21-10,
=11;

(4)13.7-9.9,
=13.7-10+0.1,
=3.7+0.1,
=3.8;

(5)98×45+2×45,
=45×(98+2),
=45×100,
=4500;

(6)56×102,
=56×100+56×2,
=5600+112,
=5712.

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