Jerome在每張卡片上寫(xiě)下1-20號(hào),將這些卡片放在盒子里面.每次從盒子里面無(wú)放回任意拿出一張卡片.為了保證他拿出的卡片上面數(shù)字之和為偶數(shù),他必須取多少?gòu)?
假設(shè)第一張是偶數(shù),接下來(lái)取的都是10張偶數(shù),那么每取一張,它們的和始終都是奇數(shù)
只有等10張偶數(shù)全部取完,接下來(lái)再取就是奇數(shù),它們的和就是偶數(shù)
所以：必須取1+10+1=12張第一張是奇數(shù)吧？對(duì)對(duì)對(duì)，是我寫(xiě)錯(cuò)了！
問(wèn)一道GMAT數(shù)學(xué)題!
問(wèn)一道GMAT數(shù)學(xué)題!
Jerome wrote each of the integers 1 through 20,inclusive,on a separate index card.He placed the cards in a box,then drew cards one at a time randomly from the box,without returning the cards he had already drawn to the box.In order to ensure that the sum of all te cards he drew was even,how many card did Jerome have to draw?
Jerome wrote each of the integers 1 through 20,inclusive,on a separate index card.He placed the cards in a box,then drew cards one at a time randomly from the box,without returning the cards he had already drawn to the box.In order to ensure that the sum of all te cards he drew was even,how many card did Jerome have to draw?
英語(yǔ)人氣：939 ℃時(shí)間：2020-04-13 10:42:57
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