The fourth proportional to 4, a and 16a is 81. What is the value of a?

This question was previously asked in
SSC CPO 2024 Official Paper-I (Held On: 27 Jun, 2024 Shift 1)
View all SSC CPO Papers >
  1. (13)/(2)
  2. (5)/(2)
  3. (9)/(2)
  4. (11)/(2)

Answer (Detailed Solution Below)

Option 3 : (9)/(2)
Free
SSC CPO : General Intelligence & Reasoning Sectional Test 1
10.3 K Users
50 Questions 50 Marks 35 Mins

Detailed Solution

Download Solution PDF

Given:

The fourth proportional to 4, a, and 16a is 81.

Formula used:

If x is the fourth proportional to 4, a, and 16a, then 4 : a = 16a : 81.

Calculation:

4 / a = 16a / 81

⇒ 4 × 81 = a × 16a

⇒ 324 = 16a2

⇒ a2 = 324 / 16

⇒ a2 = 20.25

⇒ a = √20.25

⇒ a = 4.5

∴ The value of a is 4.5 = 9/2.

Latest SSC CPO Updates

Last updated on Jun 17, 2025

-> The SSC has now postponed the SSC CPO Recruitment 2025 on 16th June 2025. As per the notice, the detailed notification will be released in due course.  

-> The Application Dates will be rescheduled in the notification. 

-> The selection process for SSC CPO includes a Tier 1, Physical Standard Test (PST)/ Physical Endurance Test (PET), Tier 2, and Medical Test.

-> The salary of the candidates who will get successful selection for the CPO post will be from ₹35,400 to ₹112,400.     

-> Prepare well for the exam by solving SSC CPO Previous Year Papers. Also, attempt the SSC CPO Mock Tests

-> Attempt SSC CPO Free English Mock Tests Here!

Get Free Access Now
Hot Links: teen patti bliss teen patti stars teen patti master apk download teen patti yes teen patti rules