EASY
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IMPORTANT
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Given that xyz=2014, and x, y and z are positive integers such that x<y<z, how many possible triples x,y,z are there?

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Important Questions on Number System

MEDIUM
IOQM - PRMO and RMO
IMPORTANT
In the following equation, each of the letters represents uniquely a different digit in base ten: YE·ME=TTT The sum E+M+T+Y equals
HARD
IOQM - PRMO and RMO
IMPORTANT
Let a, b, c, and d be positive integers such that gcda,b=24,gcdb,c=36,gcdc,d=54, and 70<gcdd,a<100. Then, find the prime number which must be a divisor of a apart from 2 and 3?
HARD
IOQM - PRMO and RMO
IMPORTANT
For a positive integer n and non-zero digits a, b, and c, let An be the n-digit integer each of whose digits is equal to a; let Bn be the n-digit integer each of whose digits are equal to b, and let Cn be the 2n-digit (not n-digit) integer each of whose digits are equal to c. What is the greatest possible value of a+b+c for which there are at least two values of n such that Cn-Bn=An2?
HARD
IOQM - PRMO and RMO
IMPORTANT

How many ordered pairs a,b of positive integers satisfy the equation a·b+63=20·lcma,b+12·gcda,b

where gcda,b denotes the greatest common divisor of a and b, and lcma,b denotes their least common multiple?

MEDIUM
IOQM - PRMO and RMO
IMPORTANT
There are 10 horses, named Horse 1, Horse 2,, Horse 10 . They get their names from how many minutes it takes them to run one lap around a circular racetrack: Horse k runs one lap in exactly k minutes. At time 0, all the horses are together at the starting point on the track. The horses start running in the same direction, and they keep running around the circular track at their constant speeds. The least time S>0, in minutes, at which all 10 horses will again simultaneously be at the starting point is S=2520. Let T>0 be the least time, in minutes, such that at least 5 of the horses are again at the starting point. What is the sum of the digits of T?
MEDIUM
IOQM - PRMO and RMO
IMPORTANT
How many ordered triples x,y,z of positive integers satisfy lcmx,y=72, lcmx,z=600 and lcmy,z=900?
HARD
IOQM - PRMO and RMO
IMPORTANT
For the greatest value of x, if 2x is a factor of 101002-4501. Find the value of x15.
EASY
IOQM - PRMO and RMO
IMPORTANT
In base 10, the number 2013 ends in the digit 3. In base 9, on the other hand, the same number is written as 2676 9 and ends in the digit 6. For how many positive integers b does the base-b representation of 2013 end in the digit 3?