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一、Joanna bought only $0.15 stamps and $0.29 stamps. How many $0.15 stamps did she buy?

(1) She bought $4.40 worth of stamps.

(2) She bought an equal number of $0.15 stamps and $0.29 stamps.

A Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C BOTH statement TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D EACH statement ALONE is sufficient.

E Statements (1) and (2) TOGETHER are NOT sufficient.

正確答案：

A

題目分析：

Joanna只買了0.15和0.29兩種價值的郵票，問她買了多少枚0.15的郵票?

單獨看條件1：總共買了價值4.4的郵票。這道題隱含著一個條件：郵票數(shù)是正整數(shù)。因為4.4分成正整數(shù)的0.29與0.15組合只有一種情況，也就是各買了10枚。所以是唯一解，條件1自己就可以滿足。

單獨看條件2：兩種郵票買了一樣的數(shù)量。沒有總價，沒有上限，無法從條件2單獨得出結果。所以條件2 not sufficient.

根據(jù)以上結論，得出答案為A。

二、The figure shown represents a board with 4 rows of pegs, and at the bottom of the board are 4 cells numbered 1 to 4. Whenever the ball shown passes through the opening between two adjacent pegs in the same row, it will hit the peg directly beneath the opening. The ball then has the probability 1/2 of passing through the opening immediately to the left of that peg and probability 1/2 of passing through the opening immediately to the right. What is the probability that when the ball passes through the first two pegs at the top it will end in Cell 2?

正確答案：

D

題目翻譯：

如果一個球穿過某一行某兩個樁中間的空間，那它一定會碰到下一行的那個樁,而每碰到一次，球往左和往右走的概率都是50%，現(xiàn)在有一個球掉進了最上面那行的兩個樁中間，請問落進最下面一行第2和第3個樁之間的“Cell2”的概率。

解題思路：

把概率累加一下就可以了。第二行就是50%/50%。第三行是25%/50%/25%。那最后一行就是12.5%/37.5%/37.5%/12.5%。所以掉進Cell2的幾率是37.5%，也就是D選項。

三、If n is a positive integer and r is the remainder when (n-1)(n+1) is divided by 24, what is the value of r?

(1) 2 is not a factor of n.

(2) 3 is not a factor of n.

A Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C BOTH statement TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D EACH statement ALONE is sufficient.

E Statements (1) and (2) TOGETHER are NOT sufficient.

正確答案：C

解題思路：

從條件1看，2不是n的約數(shù)，也就是說n是奇數(shù)，所以n+1和n-1都是偶數(shù)。

令n=1，代入(n-1)(n+1)/24得到余數(shù)為0

令n=3，代入(n-1)(n+1)/24得到余數(shù)為8

令n=5，代入(n-1)(n+1)/24得到余數(shù)為0

結果不唯一，所以不充分。

同理，條件2之下我們也可以代數(shù)來算：

令n=1，代入(n-1)(n+1)/24得到余數(shù)是0

令n=2，代入(n-1)(n+1)/24得到余數(shù)是3

令n=4，代入(n-1)(n+1)/24得到余數(shù)是15

結果亦不唯一，所以也不充分。

然后1+2，也就是說n是不能被3整除的奇數(shù)：

令n=1，代入(n-1)(n+1)/24得余數(shù)為0

令n=5，代入(n-1)(n+1)/24得余數(shù)為0

令n=7，代入(n-1)(n+1)/24得余數(shù)為0

...

結果唯一，所以1+2充分，選擇C。

好了，以上就是2020年GMAT考試《GMAT數(shù)學》每日一練（10）的全部內容了，如果各位小伙伴還有不明白的地方，可以進入幫考網(wǎng)咨詢了解哦！