A-Level Maths: D5-04 Geometric Sequences: How many terms are there?

[@jamminermit]

I assume we always have to get whole number answers with these questions. Is that right?

[@TLMaths]

Yes, as it requires you to find how many terms there are, and you can't have 10.5 terms for example

[@sughrashabir]

1÷256000÷5000=7.8125×10^-10 How do i change that. If i leave answer in memory n log it i still get 7. But why does my calculator have standard form.

[@va2065]

on the 2nd question dividing 1/256000 by 5000 gives me an annoying standard form answer and from there the final result is not a whole number. i think others are getting the same problem too seeing the comments. how do i make it not be standard form. im using the normal casio calculator

[@paulina-pl3xw]

same

[@unlockedaccount]

is it okay if you use ln instead of log and you get the same answer? or will the examiners take away marks for doing that?

[@TLMaths]

That's perfectly fine.

[@singularityhq]

I couldn't get a whole number on any calculator. How do you know to stop at 387420489?

[@TLMaths]

387459231 is the final term in the sequence, so we want to find the term that gives that value (we want to find n). So 387459231 = 1.0001*3^(n-1) where a=1.0001 and r=3. Then we want to solve that equation, which I go through in the video. I'm not sure what you mean by me knowing to stop at 387420489? Could you clarify?

[@singularityhq]

​@@TLMaths My mistake, I got confused by the notation my calculator used to display the continuing decimal places.