Question

If n straight lines terminate at a point and no two are in the same line, number of angles less than two right angles that are formed is

• A. $n-1$
• B. $\frac{1}{2}n(n+1)$
• C. $\frac{1}{2}n(n-1)$
• D. $(n+1)$

Answer 1

Answer: (C)

$\frac{1}{2}n(n-1)$

$n$ - straight lines

no two points are sane

if one point is terminated by a line

$(n-1)$ points will be left

for an angle to be form two concurrent points are needed

= no of angles less than 90 degree formed

$=\frac{\left(n\right)(n-1)}{2}$