Explanation:
If there are 3 geometric means between 120 and ¹⁵/₂, then the sequence is:
120, 120r, 120r², 120r³, ¹⁵/₂
Therefore:
120r⁴ = ¹⁵/₂
r⁴ = ¹/₁₆
r = ½
The sequence is therefore:
120, 60, 30, 15, ¹⁵/₂
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