2/3-5/6+7/12-9/20+11/30-13/42怎样简便计算
2/3-5/6+7/12-9/20+11/30-13/42怎样简便计算
2/3-5/6+7/12-9/20+11/30-13/42
=(1-1/3)-(1/2+1/3)+(1/3+1/4)-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)
=1-1/3-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7
=1-1/3-1/2-1/7
=1/6-1/7
=1/42
这是简便计算的。
2/3-5/6+7/12-9/20+11/30-13/42
2/3-5/6+7/12-9/20+11/30-13/42
=2/3-(1/2+1/3)+(1/3+1/4)-(1/4+1/5)+(1/5+1/6)-(1/6+1/7)
=2/3-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7
= 1/42
1+1/2-5/6+7/12-9/20+11/30-13/42+15/56=怎样简便计算
1+1/2-5/6+7/12-9/20+11/30-13/42+15/56 =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+..........................................................+1/8 =9/8
1-5/6+7/12-9/20+11/30-13/42+15/56-17/72简便计算
1-5/6+7/12-9/20+11/30-13/42+15/56-17/72
=1-1/2-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7+1/7+1/8-1/8-1/9
=1/2-1/9
=7/18
简便计算 1－5/6+7/12－9/20+11/30－13/42+15/56－17/72
1－5/6+7/12－9/20+11/30－13/42+15/56－17/72
=1-（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）
=1-1/2-1/9
=1/2-1/9
=9/18-2/18
=7/18
4/3+7/12-9/20+11/30-13/42简便计算
4/3+7/12-9/20+11/30-13/42
=1+1/3+11/30-9/20+7/12-13/42
=1+7/10-9/20+7/12-13/42
=1+1/4+7/12-13/42
=1+5/6-13/42
=32/21
1-1/3+7/12-9/20+11/30-13/42简便计算
1-1/3+7/12-9/20+11/30-13/42
=1-1/3+1/3+1/4-1/4-1/5+1/5+1/6-1/6-1/7
=1-1/7
=6/7
1-5/6+7/12-9/20+11/30-13/42+15/56-17/72+19/90 简便计算
1 - 5/6 + 7/12 - 9/20 + 11/30 - 13/42 + 15/56 - 17/72 + 19/90
= 1 - (3+2)/6 + (4+3)/12 - (5+4)/20 + (6+5)/30 - (7+6)/42 + (8+7)/56 - (9+8)/72 + (10+9)/90
= 1 - 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 + 1/9 + 1/10
= 1/2 + 1/10
= 5/10 + 1/10
= 6/10
= 3/5
