An AP consists of 50 terms of which 3rd term is 12 and the last term is 106. Find the 29th term.
Two APs have the same common difference. The difference between their 100th terms is 100, what is the difference between their 1000th terms?
Let the common difference of both the
A.P.’s = d
and First term of Ist A.P. = a
also first term of 2nd A .P. = b
Then, 200th term of 1st A .P. = a + 99d
and 100th term of IInd A .P. = b + 99d
Difference between their 100th term = 100
(given)
⇒ (a + 99d) – (b + 99d) = 100
⇒ a – b = 100 ...(i)
Now, a1000 of Ist A.P. = a + 999d
and a1000 of Ilnd A .P. = b + 999d
Hence, difference between their 1000th terms
= (a + 999d) (b + 999d) = a – b
= 100. [Using (i)]