SSC CGL Tier-2 11th September 2019 Maths

Question 57

When x is added to each of 2, 3, 30 and 35, then the numbers obtained in this order, are in proportion. What is the mean proportional between (x + 7) and (x - 2)?

Solution

Order after adding x,
2 + x, 3 + x, 30 + x, 35 + x
Condition of proportion,
$$\frac{2 + x}{3 + x} = \frac{30 + x}{35 + x}$$
$$(2 + x)(35 + x)  = (3 + x)(30 + x)$$
$$70 + 2x + 35x + x^2 = 90 + 3x + 30x + x^2$$
37x = 20 + 33x
x = 5
Mean proportional between (x + 7) and (x - 2) = $$\sqrt{(x + 7)(x - 2)}$$
= $$\sqrt{(5 + 7)(5 - 2)}$$
= $$\sqrt{36}$$
= 6

Share on Whatsapp Share on Whatsapp

Create a FREE account and get:

  • Free SSC Study Material - 18000 Questions
  • 230+ SSC previous papers with solutions PDF
  • 100+ SSC Online Tests for Free

cracku

Boost your Prep!

Download App