maths!!!!!!!!! p.6

2006-11-06 12:00 am

i need working and answer!!請use公式計!!!!!!!!

1) 120+110+100+......+(-20)

2)101+102+103+........+150

回答 (3)

2006-11-06 12:12 am

✔ 最佳答案

1) 120+110+100+......+(-20)=(120-20)*15/2=750

12)101+102+103+........+150 =(101+150)*50/2=6275

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2006-11-06 12:08 am

1)120-20+110-10+100x4+90
=200+400+90
=690

2)100x50+(1+50)x50/2
=5000+51x25
=5000+1275
=6275

參考: me

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2006-11-06 12:04 am

呢兩題都係關於連續數，用：
(頭+尾)*項數/2

1) (120-20)*11/2=550

2) (101+150)* 50 /2= 6275

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