I think you typed the question wrongly. It should be:
"48, 180 and k have lowest common multiple of 2160. What
is the least value of k?"
Answer:
2160 = 2^4 x 3^3 x 5
48 = 2^4 x 3
180 = 2^2 x 3^2 x 5
k = 3^3 = 27
(To find LCM, we take the number with the highest power
(index). Since 2160 has 3^3, but 48 and 180 has only 3
and 3^2, the 3^3 must be in k)