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by danjuma » Sun Oct 10, 2010 9:28 am
For any positive integer n, the lenght of n is defined as the number of prime factors whose product is n. For example , the lenght of 75 is 3, since 75 =3x 5x5, how many 2-digit positive integers have lenght 6?

a. None b. 1 c.2 d.3 e.4
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by this_time_i_will » Sun Oct 10, 2010 9:33 am
let's start with smallest two digit positive integer.
it wud be 64 = 2^6.---(i)
one more we can get by: 2^5*3...(ii).
trying to find one more: 2^4*3^2 = but this is three digit.

so we were able to find only 2.
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