Q27.If M is a positive integer, then M^3 has how many digits?

(1) M has 3 digits.

(2) M^2 has 5 digits

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 NOT sufficient

碰到这种题目怎么做？

If condition 1 and 2 combined looks promising, I generally look for 2 cases which both satisfy both conditions but have different outcomes (answer to the original question). The examples are generally boundary conditions. For example:

Case 1:
smallest M^2 is 10000 where M = 100
M^3 = 1000000, 7 digits

Case 2:
largest M^2 is 99999 where M = 300+
M^3 = 100000*300 ish = 30000000 ish, 8 digits

E