## ICSE Class 10 Maths Sum of n Terms of an A.P.

- When do we use s=n/2(a+l) formula and when do we use s=n/2 x {2a+(n-1)d} formula in the sum of a.p?
- In arithmetic progression , when we use s=n/2 [2a+(n-1)d] then why use a=(n-1)d formula?
- Given 1/(1*2*3)+1/(2*3*4)+.....+1/(98*99*100)=a/b. Find (b-a).
- mrs gupta replace her total lone of 1,18000 by paying instalments every month. if the instalment for first month is 1000 and it increase by 100 every month ? what amount of lone she still has to pay after the 30 th instalment
- the sum of first 6 terms of an A.P is 63 .The ratio of the 10th term to the 20th term is 1:2 . calculate the first and the 15th terms
- The algebraic expression of a sequence is 81-8n. What is 10th term What is the sum of 1st 10 terms whether the sum of any number of terms of the sequence will be 400? Why?
- The sum of n natural number is 5n2 - 4n, find its 8th term
- Find the sum of all even numbers between 10 and 100.
- How many terms of the A P 17,15,13,11..... must be added to get the sum 72?
- if the sum of P terms of an arithmetic progression is equal to some of its Q terms. prove that the sum if(P+Q) terms of it is equal to zero