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Question : If the points (5,5), (10,k) and (-5,1) are collinear, then k is equal to 
a) 0
b) -2
c) 8
d) 7

Doubt by Saumya 

Solution : 

Let
A(5,5)

B(10,k)

C(-5,1)

This Question can be solved by using the concept that if the points are collinear then area of triangle will be zero. But the formula for Area of Triangle is deleted in the class X Math's Syllabus of 2020-2021 so this question can't be solved by section formula or distance formula.

By the way, the value of k is 7.