Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:
The best way to solve this is to use the formulae for sum of a series.which is Sum of n terms= n/2[2a + (n-1)d] where a= first term of series which is 1 here n = no of terms which is n in first case and 2n in second case d= difference between two terms Hence Sum of n terms = n/2[2+2n-1]=n/2[n+1] Sum of 2n terms = 2n/2[2+2n-1]=n[2n+1] Difference of both = n(3n+1)/2