An integer greater than 1 that is not prime is calledcomposite. If the two-digit integer n isgreater than 20, is n composite?
(1) The tens digit of n is afactor of the units digit of n.
(2) The tens digit of n is 2.
A. Statement (1) ALONE is sufficient, but statement(2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement(1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient,but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOTsufficient.
参考答案：A
题目翻译：比1大的非质数整数叫合数，那么大于20的整数是不是合数?
题目全解：
(1) The tens digit of n is a factor of the units digit of n.
If this is true then n is NOT a prime number. This is true because if the tens digit is a factor of the units digit, the whole number will be divisible by that number because the tens digit is obviously a factor of itself! Try it out:
2X = 22, 24, 26, 28
3X = 33, 36, 39
4X = 44, 48
5X = 55
6X = 66
7X = 77
8X = 88
9X = 99
For each of these numbers the tens digit evenly goes into itself and is then a factor of the units. Impossible to have a prime number under these rules. SUFFICIENT
(2) Statement 2 tells us nothing on its own. n could be prime (23) or composite (24)
If w, x, y, and z are integerssuch that 1 < w < x < y < z and wxyz = 462, then z =?
A. 7
B. 11
C. 14
D. 21
E. 42
参考答案：B
题目翻译：wxyz大于一整数且依次从小到大，商是462，求z。
题目全解：分解462=2*3*7*11,选B。
