Answer:
210
Explanation:
As there is one circle in first row, 2 circles in 2nd row and three in third row, which clearly implies that the number of circles in each row is equal to the row number. So, we have to calculate sum of first 20 numbers to calculate the total number of circles.
n=20
Total Circles=(n(n+1))/2
=(20 (20+1))/2
=(20(21))/2
= 420/2
=210
So the total number of circles will be 210.