小学六年级数学 用简便方法计算1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72
小学六年级数学 用简便方法计算1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72
原式=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+1/8-1/9
=1-1/9
=8/9
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72=?要用简便方法做哦
1.
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(5/1-1/6)+(1/6-1/7)+(1/7-1/8)+(1/8-1/9)
=1-1/9
=8/9
2.根据各项数值的特点寻找规律,会发现:1/2=1-1/2,1/6=1/2-1/3......,把各项都化成统一形式即可进行简便计算。
数学题 1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72=?
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72
=1-1/2+1/2-1/3+……+1/8-1/9
=1-1/9
=8/9
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72怎样用简便
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72
=(1/1)*(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)+(1/8)*(1/9)
=(1-1/2)+(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)+(1/8-1/9)
=1-1/9
=8/9
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72 怎么样算才简便
1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72
=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+1/8-1/9
=1-1/9
=8/9
1/1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72怎么算
1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=加一个1/2减一个1/2,加一个1/3减一个1/3,加一个1/4减一个1/4,加一个1/5减一个1/5,依次类推
=还是下1-1/9
=8/9
其实这样的题很简单,我今天月考,也有这样的题,老师都讲了,只要动动脑筋就行了。
希望对你有帮助,希望采纳。
1/2+1/6+1/20+1/30+1/42+1/56+1/72=怎么算简便?
用拆项法
1/2+1/6+1/20+1/30+1/42+1/56+1/72
=1/(1*2)+1/(2*3)+1/(4*5)+1/(5*6)+1/(6*7)+1/(7*8)+1/(8*9)
=1-1/2+1/2-1/3+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
=1-1/3+1/4-1/9
=7/12
不过照常规来说,应该有1/12这一项的,是不是少打了,反正方法是一样的,拆项相消。