Question

六年级奥数题，速算巧算。

1. (1.3×3.9×11.7＋3×9×27＋1/17×3/17×9/17)/(1.3×2.6×3.9＋3×6×9＋1/17×2/17×3/17)
2. 2/3＋2/9＋2/27＋2/81＋2/243
3. 1＋2＋3＋4＋5＋6＋7＋8＋9＋8＋7＋6＋5＋4＋3＋2＋1/999999999²
4. 2×3×4×5＋5×6×7×8/2×3×4×5
5. (1＋1/2＋1/3＋1/4)×(1/2＋1/3＋1/4＋1/5)－(1＋1/2＋1/2＋1/4＋1/5)×(1/2＋1/3＋1/4)

Answer 1

1. (1.3×3.9×11.7＋3×9×27＋1/17×3/17×9/17)/(1.3×2.6×3.9＋3×6×9＋1/17×2/17×3/17)
=[1.3×(1+3+9)+3×(1+3+9)+1/17 ×(1+3+9)]/[1.3×(1+2+3)+3×(1+2+3)+1/17 ×(1+2+3)]
=(1.3+3+1/17)(1+3+9)/(1.3+3+1/17)(1+2+3)
=(1+3+9)/(1+2+3)
=13/6

2. 2/3＋2/9＋2/27＋2/81＋2/243
=2/243 ×(81+27+9+3+1)
=2/243 × 121
=242/243

4. 2×3×4×5＋5×6×7×8/2×3×4×5
=120+14
=134

5. (1＋1/2＋1/3＋1/4)×(1/2＋1/3＋1/4＋1/5)－(1＋1/2＋1/3＋1/4＋1/5)×(1/2＋1/3＋1/4)
设1/2＋1/3＋1/4＝t
原式可化为
(1+t)(t+1/5)-(1+t+1/5)t
=1/5

Answer 2

你好： 98989898×99999999÷10101010÷11111111 =(98989898÷10101010)×(99999999÷11111111) =9.8×9 =88.2 12.9÷0.72＋43.5÷3.6 =64.5÷3.6

追问

我的意思是帮我做一下问题补充里的题！！！

Answer 3

看1LLZ啊

Answer 4

一楼是对的