Question

Triangle is formed by the coordinates (0, 0), (0, 21) and (21, 0). Find the number of integral coordinates strictly inside triangle (integral coordinates has both x and y):

• A. 190
• B. 105
• C. 231
• D. 205

Answer 1

The correct option is A

190

Number of points with integral co-ordinates that are inside the triangle formed by (0,0), (n, 0)

And (0,n) is $\frac{(n-1)(n-2)}{2}$

$\therefore$ Required points =190