估算397×11≈ 207×99≈ 190×31≈49×62≈ 504×51≈ 91×68≈
×80% 1﹣78% 100﹣56%÷40% 60%×70% 8.7×45% 1+1% 25×． 1.2+20%+×90% 8×（1+25%） 80%÷．
口算 15÷0.25= 1.5×=×1.8= 2.5×0.4= 32×2.5= 24×= 2.4+1.6=÷=×=÷25%=
直接写得数． 2.4×50%=+= 5.8﹣0.89= 0.52=÷10= 3.9×1.1=（+）×12= 1﹣+=
3.26+2.4=== 3.6÷0.6= 1﹣0.52= 2.5×3.5×0.4===
直接写得数：×0.87=÷1.2=÷= 0.56×= 2006﹣619= 6﹣= 3.2×= 0.3×0.4= 2.85+1.5= 73.05﹣3.96==== 1÷×= 7×÷7×=
×80% 1﹣78% 100﹣56%
÷40%
×90% 8×（1+25%） 80%÷
=
×1.8= 2.5×0.4= 32×2.5=
= 2.4+1.6=
÷
=
×
=
÷25%=
+
= 5.8﹣0.89= 0.52=
÷10= 3.9×1.1=（
+
）×12= 1﹣
+
=
=
= 3.6÷0.6=
=
=
×0.87=
÷1.2=
÷
= 0.56×
= 2006﹣619=
= 3.2×
= 0.3×0.4= 2.85+1.5= 73.05﹣3.96=
=
=
= 1÷
×
= 7×
÷7×
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