凹凸学园第二季免费20

甄怡享19181/2+5/6 - 7/12+9/20 - 11/30+13/42 - 15/56 -
谭阮狐19169032906 ______ 1/2+5/6-7/12+9/20-11/30+13/42-15/56 =1/2+(1/2+1/3)-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)-(1/7+1/8) =1/2+1/2-1/8 =7/8

甄怡享1918简算:1/2+1/6+1/12+1/20+……+1/90 -
谭阮狐19169032906 ______ 1/2+1/6+1/12+1/20+……+1/90 =1-1/2+1/2-1/3+...+1/9-1/10 =1-1/10 =9/10

甄怡享19181/1*3*5+1/2*4*6+...........1/20*22*24 -
谭阮狐19169032906 ______ 1/[n(n+2)(n+4)]=0.125/n-0.25/(n+2)+0.125/(n+4) 原式为1/1*3*5=0.125/1-0.25/3+0.125/51/2*4*6=0.125/2-0.25/4+0.125/6....1/20*22*24=0.125/20-0.25/22+0.125/24 加起来就是 原式=0.125*(1+1/2+1/3+...+1/20)-0.25*(1/3+1/4+1/5+...+1/22)+0.125*(1...

甄怡享1918坐火车可以带香水吗? -
谭阮狐19169032906 ______ 香水不能带上火车,因为香水的溶剂一般是有机溶剂,有机溶剂属于易燃物,所以不能带. 香水中香精用量较高,一般为15%~25%,乙醇浓度为75%~85%,火车上禁止带乙醇类易燃易爆物品,所以不能带上车. 铁路部门规定,请勿携带易燃...

甄怡享1918被减数是15,减数是2,差是多少 -
谭阮狐19169032906 ______ 被减数是15,减数是2,差是13. 过程: 被减数-减数=差, 被减数是15,减数是2, 由公式得知: 差=被减数-减数 =15-2 =13

甄怡享19181\3+1\15表示2\5,用1\4+1\7+1\28表示3\7等,现有90个分数:1\2,1\3,1\4…,1\90,1\91,挑10个加正负号,使和= - 1 -
谭阮狐19169032906 ______ -1/2-1/6-1/12-1/20-1/30-1/42-1/56-1/72-1/90-1/10=-1 方法;1/(1*2)+1/(2*3)+1/(3*4)+……+1/(9*10)+1/10 =(1/1-1/2)+(1/2-1/3)+(1/3-1/4)+……+(1/9-1/10)+1/10 =1 把它们都变成相反数即可. 也可以: -1/2-1/5-1/14-1/20-1/21-1/24-1/28-1/40-1/60-1/...

甄怡享19181/2+1/6+1/12+1/20+1/30简便计算 -
谭阮狐19169032906 ______ 1/2+1/6+1/12+1/20+1/30=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+1/(5*6)=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6=1+(1/2-1/2)+(1/3-1/3)+(1/4-1/4)+(1/5-1/5)-1/6=1-1/6=5/6

甄怡享1918a、b、c三个数的平均数是180,a是b的2倍,c比a多20,三个数各是多少?
谭阮狐19169032906 ______ a: (180*3-20)÷(2+1+2)*2 =(180*3-20)÷5*2 =520÷5*2 =208 b: (180*3-20)÷(2+1+2)*1 =(180*3-20)÷5*1 =520÷5*1 =104 c: (180*3-20)÷(2+1+2)*2+20 =(180*3-20)÷5*2+20 =520÷5*2+20 =228 验算: (208+104+228)÷3 =540÷3 =180 a、b、c三...

甄怡享1918两堆煤共重160吨,如果甲堆运走2/5多20吨,乙堆运走2/5少6吨,那么两堆煤共运走多少吨? -
谭阮狐19169032906 ______ 甲乙共运走了总数的2/5多20-6=14吨 两堆煤共运走160*2/5+14=78吨

甄怡享19181/2+1/6+1/12+1/20+........+1/110=? -
谭阮狐19169032906 ______ 解答: 1/2+1/6+1/12+1/20+........+1/110=1/(1*2)+1/(2*3)+1/(3*4)+1/(4*5)+........+1/(10*11)=1/1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+......+1/10-1/11=1-1/11=10/11