Question
Question: Let r, s, t be 3 distinct prime numbers and L.C.M. of 2 positive integers p and q is r<sup>2</sup>s<...
Let r, s, t be 3 distinct prime numbers and L.C.M. of 2 positive integers p and q is r2s4t2. Then the no. of ordered pairs (p, q) can be formed is
A
220
B
222
C
224
D
218
Answer
224
Explanation
Solution
No. of ordered pairs =
((3 + 3) - 1) ((5 + 5) -1) ((3 + 3) -1) - 1
= 5 x 9 x 5 - 1 = 224.