请用简便计算来算出结果 梯等式,12.5×19.7×3.2 2.5×9.7—9.7×0.4 7.8×

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12.5×19.7×3.2
=12.5×19.7×8×0.4
=12.5×8×19.7×0.4
=100×19.7×0.4
=197×4
=7882.5×9.7—9.7×0.4
=9.7×(2.5-0.4)
=(10-0.3)×2.1
=10×2.1-0.3×2.1
=21-0.63
=20.37
7.8×0.98
=7.8×(1-0.02)
=7.8-0.156
=7.644
68.34×1.4÷68.34×50
=68.34÷68.34×1.4×50
=1×1.4×50
=7015÷7.5÷0.2×4.5
=2÷0.2×4.5
=10×4.5
=45======以下答案可供参考======
供参考答案1:
7.8×0.98
=7.8X（1-0.02）
=7.8X1-7.8X0.02
=6.36