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# A quick question about geometric sequences and logarithms watch

1. So I have worked with logarithms before and I definitely now about geometric sequences, but I got a question about both together on a practice test today and I had no idea how to get the answer.

The question was: A geometric sequence has first term 5 and common ratio 7.
The kth term is 28 824 005.
Use logarithms to find the value of k.

Thanks
2. (Original post by gavinfourie)
So I have worked with logarithms before and I definitely now about geometric sequences, but I got a question about both together on a practice test today and I had no idea how to get the answer.

The question was: A geometric sequence has first term 5 and common ratio 7.
The kth term is 28 824 005.
Use logarithms to find the value of k.

Thanks
We can only give you hints in the Maths forum.

So we know a = 5 and r = 7 and the formula for the kth term is ....

Put that equal to 28 824 005 and post your equation.

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Updated: January 25, 2017
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