狗二七六

sli725 · 发表于 2011-1-13 19:17:22

276. a,b,d三个连续的正整数，a<b<c 貌似问能不能确定a,b,c的值

条件1：bc-ab=12 条件2：a+b+c=18

参考答案：D

思路：因为是3个连续的正整数，所以任何一个条件均可以转化成一个未知数的等式。

条件1，b(c-a)=2b=12，充分

条件2，3b=18，充分

这题不是告诉你ＡＢＣ是三个连续，是ＡＢＤ

选Ｃ

xihuanbinfen · 发表于 2011-1-13 19:28:00

if ABD is consecutive,then b=a+1
1)bc-ab=b(c-a)=(a+1)(c-a)=12 insufficient
2)a+b+c=a+a+1+c=2a+c=18 insufficient
1)+2) c=18-2a take this into 1） (a+1)(18-3a)=12==>a=5==>b=6==>c=7

sli725 · 发表于 2011-1-13 21:12:00

the explanation from LS freaking RULES! it is C.

but it wuda probly take you 3 mins to solve the number. my version is that (1) apparently not enough
(2) you know....
Hence taken together the two conditions give you: 1. d-b=1
2.b-a=1
3. bc-ba=12
4. a+b+c=12
Having 4 equations with 4 unknows, you can get the results.
If this doesnt work, one thing can be sure that those douche bags at G**C are buncha either fucking homos, poopheads, dumbasses, or goddamn morons. anyway, thanks a lot for you to type it in English. lota easier for me to comprehend. again, appreciate it and good luck on the preparation whether you need it or not.

xihuanbinfen · 发表于 2011-1-13 21:18:15

by the way,you should pay attention to the results of equtions,sometimes the results may not apply to the condition.for example,the roots of the equation are negetive but the nonnegative ones are needed, thus the problem can not be solved.

sli725 · 发表于 2011-1-13 21:22:47

thats exactly what i was talkin'bout. if they are not solvable and thus I gota really do the math GMAC sucks.

sli725 · 发表于 2011-1-13 21:31:16

and i saw your another post. you know what kills you? not the GMAT itself. it is yr restlessness that kills you. as my favor show says---sit tight and discusssion! i have two self- created mottos from which you might get some reliefs---1, KISMIF(KEEP IT SIMPLE N MAKE IT FUN); 2, I AM AWESOME!

xihuanbinfen · 发表于 2011-1-13 22:28:09

do you have QQ or MSN?

sli725 · 发表于 2011-1-13 23:16:29

MS suspended my MSN for some reason, my spype is, wait a sec, i'll pm you

狗二七六

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