F.1 math (MC)

2007-07-30 5:52 am

1. If a,b,c are in arithmetic sequence,which of the following is/are ture?
(1) a+1,b+2,c+3 are in arithmetic sequence.
(2) a-1,b-1,c-1 are in arithmetic sequence.
(3) 2a,2b,2c are in arithmeic sequence.

A. (1)only
B. (1) and (2) only
C. (2) and (3) only
D. All of the above

2.A rectangular block of length 27 cm and height 13cm.If the total surface area is 1182cm square ,find its width and volume.

A. 6cm,4212cm^3
B. 12cm,2106cm^3
C. 6cm,2106cm^3
D. 12cm,4212cm^3

回答 (2)

toyszchun

2007-07-30 6:14 am

✔ 最佳答案

1.
C. (2) and (3) only

2.
B. 12cm,2106cm^3

3.
C. 2cm×5cm

4.
C. (3,1)

遲些給你解釋~~

2007-07-29 22:28:53 補充：
1.a,b,c are in arithmetic sequenceLet b=a＋D , c = a ＋ 2D , where D is the common difference between each term(1)If a＋1,b＋2,c＋3 are in arithmetic sequence , (b＋2) - (a＋1) = (c＋3) - (b＋2)LHS=(b＋2) - (a＋1)=a＋D＋2-a-1=D＋1

2007-07-29 22:29:19 補充：
RHS=(c＋3) - (b＋2)=a＋2D＋3 -a-D-2=D＋1=LHS∴我剛才錯了,(1)也是對的用同樣的方法,可以試到(2),(3)也是對的所以答案是""D. All of the above"

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ah鈴

2007-07-30 11:51 pm

1C

2B

3C

4C

參考: 自己計的

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