一道DS,帮帮忙!!

jojofgasw

刚接触,题很简单,不要笑我!!

1/A+1/B+1/C=?

STATE1):ABC=24

STATE2):AB+BC+AC=26

答案选1+2,为什么不是2??

谢谢!!!

teyvhf

1) abc = 24

2) ab + bc + ac = 6, by dividing abc on both sides, we can get 1/c + 1/a + 1/b = 6/abc, thus it's not sufficient to tell what the answer is(since we have no idea what 6/abc is whithout knowing 1)), thus 2) is not suffiicent by itself

and 1) and 2) are needed in order to know the answer

thus the answer is C <= thanx susan