1. Arithmetic Progressions
by M. Bourne
We want a sequence of numbers. Let's start with a number: `a_1`.
Now add a number `d`, (for "difference").
We get `a_1 + d` and the first 2 terms in our sequence are:
`a_1 + d`
For the next term, let's add another `d` to that last term and we have `a_1 + 2d`.
Our sequence is now:
`a_1 + d`,
`a_1 + 2d`
We continue this process for as long as we can stay awake. The resulting set of numbers is called an arithmetic progression (AP) or arithmetic sequence.
Let's start with `a_1 = 4` and then add `d=3` each time to get each new number in the sequence. We get:
`4, 7, 10, 13, ...`
General Term of an Arithmetic Progression
The nth term, `a_n` of an AP is:
Sum of an Arithmetic Progression
The sum to n terms of an AP is:
`S_n=n/2(a_1+a_n)\ or\ S_n=n/2[2a_1+(n-1)d]`
Using the second formula, find the sum of the first 10 terms for the series that we met above: `4, 7, 10, 13, ...`
Find the sum of the first
`1000` odd numbers.
A clock strikes the number of times of the hour. How many strikes does it make in one day?