从1,2,3,4,5,6,7,8,9,10这10个数中,任取5个数相加的和与其余5个数相加的和相乘,能得到多少个不同的乘积?
(1)100﹣98+96﹣94+92﹣90+…+8﹣6+4﹣2 (2)1001×1001﹣1001.
3+6+9+…++300+3031999+999×9991.24×0.25+124×750.8888×6+0.1111×52.
计算: ①3×(x+9)=27 ②16×8﹣7x=23 ③7.5﹣7.5×0.5﹣2.6×0.8 ④13.7×6.5+5.9×13.7﹣12.4×3.7 ⑤50×[(0.2+4.8﹣4.8+0.2)÷2] ⑥11.25+21.25+31.25+41.25+51.25+61.25+71.25+81.25.
计算下列各题 ①×+25%×+0.25×②[1﹣(+)]÷ ③9.6﹣11÷7+×4 ④.
计算(能简算要简算) (1)(2) (3)(4).