Mathematics 9709 · AS & A Level · Series

Series — practice question

(i)[2]

The first two terms of a geometric progression are $p$ and $2p$ respectively, where $p$ is a positive constant. The sum of the first $n$ terms is greater than $1000p$. Show that $2^n > 1001$.

(ii)[5]

In a different case, $p$ and $2p$ are the first and second terms of an arithmetic progression respectively. The $n$th term is $336$ and the sum of the first $n$ terms is $7224$. Write down two equations in $n$ and $p$ and hence find the values of $n$ and $p$.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: Use the sum formula $S_n=\frac{p(2^n-1)}{2-1}$ for the progression.

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