Solution
The general form of the n-th term = a + (n-1)d
Here we are given the 1st term (a) = 10
6th term = 40
We need to find the 20th term.
Let's find the common difference.
6th term = 10 + (6 - 1) d
6th term is 40, so
40 = 10 + (6 -1)d
40 -10 = 5d
30 = 5d
d = 30/5
d = 6
The common difference is d = 6.
20th term = a + (n -1)d
= 10 + (20 -1)6
= 10 + 19*6
= 10 + 114
20th term = 124
