Question

How do you find the common ratio for `7,14,28,56,128,...`?

Answer 1

Ignoring the `128` (which should probably have been `112`), the common ratio is `2`.

Explanation:

For this sequence to have a common ratio, the ratio between any pair of consecutive terms must be the same.

So if this sequence does have a common ratio, then we can look at any pair of consecutive terms, e.g. `7, 14` to find the ratio:

`14/7 = 2`

This ratio is the same for `28/14` and `56/28`, but `128 != 2*56`.

I suspect a typo in the question. The value you would expect is `112` rather than `128`.