发布人:繁体字网(www.fantiz5.com) 发布时间:2015-10-24 07:30:00
试题原文 |
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①3×(x+9)=27, 3x+27=27, 3x+27-27=27-27, 3x=0, x=0; ②16×8-7x=23, 128-7x=23, 128-7x+7x=23+7x, 23+7x=128, 23+7x-23=128-23, 7x=105, 7x÷7=105÷7, x=15; ③7.5-7.5×0.5-2.6×0.8, =7.5×(1-0.5)-2.08, =7.5×0.5-2.08, =3.75-2.08, =1.67; ④13.7×6.5+5.9×13.7-12.4×3.7, =13.7×(6.5+5.9)-12.4×3.7, =13.7×12.4-12.4×3.7, =(13.7-3.7)×12.4, =10×12.4, =124; ⑤50×[(0.2+4.8-4.8+0.2)÷2], =50×{[(0.2+0.2)+(4.8-4.8)]÷2}, =50×[0.4÷2], =50×0.2, =10; ⑥11.25+21.25+31.25+41.25+51.25+61.25+71.25+81.25, =(11+21+31+41+51+61+71+81)+0.25×8, =[(10+20+30+40+50+60+70+80)+8]+2, =[(20+80)+(30+70)+(40+60)+(10+50)]+(8+2), =300+60+10, =370. |
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