The third term of an A.P is 10 and the sixth term is 43 find: the 20th term with shown working
The common difference of an A.P is the same between each term.
Therefore, the common difference is (43 - 10) / (6 - 3) = 33/3 = 11.
The 20th term is found by adding 11 to the 19th term.
The 19th term is 10 + (19 - 3) x 11 = 10 + 16 x 11 = 10 + 176 = 186.
Therefore, the 20th term is 186 + 11 = 197.