幾條數學問題,,,請幫幫手

1)
50.5+49.6+48.7+47.8+46.9+45.10+44.11+43.12+...6.49+5.50
= [50 + 49 + 48 +...+ 6 + 5] + [0.5 + 0.6 + ...+ 0.49 + 0.50]
= [50 + 49 + 48 +...+ 6 + 5] + 0.1 x [50 + 49 + 48 +...+ 6 + 5]
= (1 + 0.1) x [50 + 49 + 48 +...+ 6 + 5]
= 1.1 x (5 + 50) x 46 / 2
= 1.1 x 55 x 23
= 1391.5
2)
849999/17+84999/17+8500/17+851/17+86/17
= (850000 - 1)/17 + (85000 - 1)/17 + 8500/17 + (850 + 1)/17 + (85 +1)/17
= 850000/17 - 1/17 + 85000/17 - 1/17 + 8500/17 + 850/17 + 1/17 + 85/17 + 1/17
= 50000 + 5000 + 500 + 50 + 5 - 1/17 - 1/17 + 1/17 + 1/17
= 55555

2008-08-10 22:30:43 補充：
1)

50.5+49.6+48.7+47.8+46.9+45.10+44.11+43.12+...6.49+5.50

= [50 + 49 + 48 +...+ 6 + 5] + [0.5 + 0.6 + ...+ 0.49 + 0.50]

= [50 + 49 + 48 +...+ 6 + 5] + 0.01 x [50 + 49 + 48 +...+ 6 + 5]

= (1 + 0.01) x [50 + 49 + 48 +...+ 6 + 5]

= 1.01 x (5 + 50) x 46 / 2

= 1.01 x 55 x 23

= 1277.65

第一條數字無連貫性
無左47.08 (我估)
數字題目九成打錯 (唔係 50.5 . 應係50.05)
我估條數係咁
50.05+49.06+48.07.....+5.50
如果係咁, 整數整數計, 點數點數計就可以.
將5加到50, 總數46個
條數係 (5+50)*46/2 =1265
點數都係呢組,加埋係 12.65
所以總數係 1277.65

2) 17*5 =85
條數係想你咁計
849999/17 = 50000 - 1/17
84999/17 = 5000 - 1/17
8500/17 = 500
851/17 =50 +1/17
86/17 = 5 + 1/17

咁加埋就係55555

1.
50.5+49.6=100.1
100.1+48.7=148.8
148.8+46.9=195.7
195.7+45.10=240.8
240.8+44.11=284.91
284.91+43.12=328.03
328.03+6.49=334.52
334.52+5.50=(340.02)
最後答案=340.02