Question

小学数学题求解,答案对就采纳求1/12,2/12,3/1,4/12……,239/12这239个数中所有不是整数的分数的和

Answer 1

首先239/12 < 20于是 1/12 + 2/12+3/12+.239/12 = (1 +2+3.+239)/12 -(1+2+3.+19) = ((1+239)X239)/(2X12) - ((19+1)X19)/2 =2390 - 190 =22002. 3321 /20 ÷ 41 =（3321 /41）/20= 81/20

3.（-1/3+7/12-9/20+11/30-13/42+15/56）×21

= -1/3+(3+4)/(3x4)-(4+5)/(4x5)+(5+6)/(5x6)-(6+7)/(6x7)+(7+8)/(7x8)）×21

=（-1/3+(1/3+1/4)-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)+(1/7+1/8)）×21

=21/8

=2.625