If the sums of n terms of two arithmetic progressions are in the ration $$\frac{{3n + 5}}{{5n + 7}},$$   then t…

The sum of first five multiples of 3 is:

The 7<sup>th</sup> and 12<sup>th</sup> term of an arithmetic progression are -15 and 5 respectiv…

The sum of first 20 odd natural numbers is

The first and last terms of an A.P. are 1 and 11. If the sum of its terms is 36, then the number of terms will be

(1) + (1 + 1) + (1 + 1 + 1) + ....... + (1 + 1 + 1 + ...... n - 1 times) = ......

If the first, second and last term of an A.P. are a, b and 2a respectively, its sum is

15<sup>th</sup> term of A.P., x - 7, x - 2, x + 3, ........ is