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This problem trains for: SAT-I, AMC-8, GMAT, AMC-10.
In a geometric sequence the ratio between the 8th and the 6th terms is 25. The 4th term is divisible by:
If the first term of the sequence is a0 and the ratio is r, use the Nth term formula (or just reasoning) to write prototypes for the 8th and 6th terms:
The ratio of the two terms is:
and the ratio of the sequence can be derived to be one of:
The fourth term could be one of:
which is always divisible by 125.