GMAT 数学题（6）

youngerlee

你知道数字 24 所有因子的和是多少吗？我可以告诉你是60。那你能告诉我数字 1800 所有因子的和是多少吗？

1) 4500
2) 5040
3) 6000
4) 6045
5) 6666

bettyofariN

1+2+3+4+6+8+12+24 =60

queenie924

#1 24=2^3*3  sum of factors can be enumerate in this equation, perhaps.
(2^0+2^1+2^2+2^3)*(3^0+#^1)=!+24+2+12+3+8+4+6

So, let's talk about 1800. 因式分解省略
#2 (2^0+2^1+2^2+2^3)(3^0+3^1+3^2)(5^0+5^1+5^2)=15*13*31=6045

i choose 4)

haileywang

1800=2^3x3^2x5^2

1800因子之和=(1+2+4+8)(1+3+9)(1+5+25)=6045

youngerlee

Great.  You guys are quick and smart.

cckjenius

弱问，考试有没有这么难啊~

youngerlee

Probably not this hard.  

But GMAT does ask about the sum of all even numbers between 100 and 200, as well as the number of factors for a particular integer. It is not rocket science to
combine the two types of questions together and form a new type of question.

Besides, it is the mental training and logic thinking that will be tested during the real exam.  Figuring out ways to solve tough questions might sharpen your
skills and prepare your mind for the real test.