[转帖]北美4月16 - 710(M50V36)

smart

Math old JJ: #8 (eclipse area), #11 (ccircle), #15, #16, #30, #35, #39,
#53 (variant: the questions shows the result is 350 for all the digits
of number 10^n - 52, show n=?), #63,

One math question: ask if x > x2?
1). x > 0.  2), x > 1
f(x) = x - x2 = x(x-1) > 0 ==> x > 1 or 0 < x < 1
therefore, if x > 1, it is clearly that f(x) > 0, so the answer is B.

Another math question: which number is most closest to 1/2? choices are: 4/7, 5/9, 6/11, 6/13, 9/16
solution:
calculate the result of each number substract 1/2, and the result is
obvious, should be the 6/13 one (that one results in 1/26), which is
the smallest among all the substrated results.

another one is
similar to #93, but the question is: seniors only (20), chemistry only
(xx), there is a condition says the total chemistry students are
something, from which we can know that the common area of (senior and
chemistry) is 4, ask: what percenatge of seniors are in chemistry? 4/24
= 16.67%