Hi all, I'm new to this website, really pleased to have found such a great website to satisfy my mathematical and scientific queries and doubts! anyway, I am currently revising for major tests.. and I can't understand/solve questions regarding Arithmetic/Geometric Progression (if you know what this topic means). Do help if possible :) 1. The problem statement, all variables and given/known data so here are a few of those head crippling questions: 1) The sum of the first 100 terms of an arithmetic progression is 15050; the first, third and eleventh terms of this progression are three consecutive terms of a geometric progression. Find the first term, a and the non-zero common difference, d, of the arithmetic progression. 2) At the beginning of the year, George deposited $100,000 with a bank that pays 10% interest per annum at the end of each year. After the interest is credited, he immediately withdraws $12,000. Likewise, George will again withdraw $12,000 at the end of each subsequent year, immediately after the bank's interest has been credited. After his n-th withdrawal, he noticed, for the first time, that his bank account balance falls below $20,000. Find n. 2. Relevant equations 3. The attempt at a solution Right, my attempts at solving this problem are entirely or mostly based on trial-and-error, and though I have gotten the answers through this tedious method.. let's just say that it is highly doubtful that it will work during the time-limited tests. What I need are concise steps that will enable me to solve these problems methodically. Thanks for your muchly appreciated help!