00:01
We're being asked to find the sum of this series.
00:03
So let's list what we know.
00:05
When we know the first term is equal to 8, so a sub 1 is equal to 8, and the last term is 50, so a sub n is equal to 50.
00:13
Now, we can also find how we get from one turn to next.
00:17
We simply add 1 .4th.
00:20
Therefore, the common difference in this particular series is 1 .4th.
00:25
So what we need to do is we need to find our n value.
00:29
To do this, we're going to use the formula to find the mth term.
00:32
In an arithmetic sequence, which remember is a sub m equals a sub 1 plus the quantity of n minus 1 times d.
00:40
So let's substitute in the values that we know.
00:44
So when we do this, we're going to get 50 is equal to 8 plus the quantity of n minus 1 times 1 4.
00:53
So let's solve for n.
00:54
To do this, i'm going to subtract 8 from both sides, and 50 minus 8 is 42...