有红、黄、绿、黑5种颜色的小球各若干个，一些同学从中取球，每个人可以任选2个，至少有多少人才能保证有2人选的小球完全相同？
直接写出得数1800﹣799= 560÷8×7= 1÷0.04= 8×125%=0.3×0.3÷0.3×0.3= ÷60%= ：= 4.6÷0.2=
在图中涂色（或画阴影）表示出．
3.2÷0.01==5.6+3.99=1.7÷2.5=2×9.9====
直接写出得数 410﹣210= = 72.8÷0.8= =1.375﹣= = = 5.2+0.54+0.46=
口算．800﹣250= 30×40= 8100÷900= 10﹣0.98= 105÷7= 560+770=0.25×0.4= 6.3÷0.07= 0.64÷8= 8.85×10= 4.73+0.7= == = = 3.6×= 8×1.36×1.25= 7.2×2.8+2.8×0.8=
÷60%= ：
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= 72.8÷0.8= 
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= 5.2+0.54+0.46=
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= 3.6×
= 8×1.36×1.25= 7.2×2.8+2.8×0.8=
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