To get the geometric mean of two numbers, multiply them and take the square root:
√(3 * 48)
= √144
= 12
Now I think it wants you to find the two geometric means of 3 & 12, and then 12 & 48:
√(3 * 12)
= √36
= 6
√(12 * 48)
= √576
= 24
Answer:
3, 6, 12, 24, 48
12..