Step 1) First we find and list the prime factors of 3, 4, and 84 (Prime Factorization):
Prime Factors of 3:
3
Prime Factors of 4:
2, 2
Prime Factors of 84:
2, 2, 3, 7
Step 2) Then we look at the frequency of the prime factors as they appear in each set above. List each prime factor the greatest number of times it occurs in any of the sets:
2, 2, 3, 7
Step 3) Finally, we multiply the prime numbers from Step 2 together.
2 x 2 x 3 x 7 = 84
That's it. The Least Common Multiple (LCM) of 3, 4, and 84 is 84.