The first term of an A.P. is 5, the last term is 45 and the sum is 400.

(i) The first term of an A.P. is 5, the last term is 45 and the sum is 400. Find the number of terms and the common difference.
(ii) The sum of the first 15 terms of an A.P. is 750 and its first term is 15. Find its 20th term.

Solution:

Solve for x : 1 + 4 + 7 + 10 + … + x = 287.

Solution:

More Solutions:

• Find the values of a and below.
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