Question

The sum of first 13 terms of an

a.P. Is 21 and the sum of first 21 terms is 13. The sum of first 34 terms is

Answer 1

Step-by-step explanation:

13 terms sum is 21 and 21 turms sum is 13 so

we applying logic that type

2+1=3 and take 1 from last no

so 13

now 3+4=7 and take 4 from last so ans is 47