PrepRung
Sign inSign up free

NDA 2021 Maths · Mathematics · Straight Lines · medium

The distance between the parallel lines 3x+4y=7 and 3x+4y=-8 is

Single correct option

The distance between the parallel lines 3x+4y=73x+4y=7 and 3x+4y=−83x+4y=-8 is
  1. A. 33
  2. B. 15\dfrac15
  3. C. 15⋅3\dfrac{1}{5}\cdot3
  4. D. 1515
Show answer and solution

Answer: (A) 33

For ax+by+c1=0ax+by+c_1=0 and ax+by+c2=0ax+by+c_2=0 the distance is ∣c1−c2∣a2+b2\dfrac{|c_1-c_2|}{\sqrt{a^2+b^2}}. Writing the lines as 3x+4y−7=03x+4y-7=0 and 3x+4y+8=03x+4y+8=0 gives 155=3\dfrac{15}{5}=3. The value 15 forgets the denominator.
Report a mistake

Original question written in the NDA 2021 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake