- Home
- Standard 11
- Mathematics
9.Straight Line
medium
The number of integral points (integral point means both the coordinates should be integer) exactly in the interior of the triangle with vertices $(0, 0), (0, 21)$ and $(21, 0)$, is
A
$133$
B
$190$
C
$233$
D
$105$
(IIT-2003)
Solution

(b) $x + y = 21$
The number of integral solutions to the equation $x + y < 21$ i.e., $x < 21 – y$
$\therefore$ Number of integral co-ordinate
$ = 19 + 18 + …. + 1 = \frac{{19 \times 20}}{2} = 190$.
Standard 11
Mathematics