Question

If line joining (1, 2) and (5, 7) is parallel to line joining (3, 4) and (11, x).

(a) 10

(b) 11

(c) 12

(d) 14

This question was addressed to me in an online quiz.

This intriguing question comes from Various Forms of the Equation of a Line topic in section Straight Lines of Mathematics – Class 11

Answer 1

Right option is (d) 14

The explanation is: We know, slope of line joining two points (x1, y1) and (x2, y2) is given by(y2-y1)/(x2-x1).

Lines are parallel means slope is equal.

=>(x-4)/(11-3) = (7-2)/(5-1) => x-4 = 5*8/4 = 10 => x=14.