Geometric progression

5 sentences makes Geometric progression. their multiplying is 243.
how much is the multiplying first sentence and fifth sentence?

I think what you mean is this:

Given that a geometric series of 5 terms multiplies to 243, what is the product of the first and fifth term?

The product of 5 terms of a geometric series is . The product of the 1st and 5th terms is , which is equal to . Hence the product of the 1st and 5th terms is . Since , this becomes .