Sum of a number and twice its square is 105. Find out that number?

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  1. 9
  2. 7
  3. 5
  4. 6

Answer (Detailed Solution Below)

Option 2 : 7
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Given: The sum of a number and twice its square is 105.

Let the number be denoted as x.

Concept Used:

The problem involves solving a quadratic equation using trial and error or logical substitution.

The equation can be represented as: x + 2x² = 105

Calculation: Start solving the equation step by step:   x + 2x² = 105

⇒ Substitute x = 7: 7 + 2 × 7² = 105

This satisfies the equation.

Final Answer:

∴ The correct number is x = 7.

Latest Army Havildar SAC Updates

Last updated on Jul 1, 2025

-> The Indian Army has released the Exam Date for Indian Army Havildar SAC (Surveyor Automated Cartographer).

->The Exam will be held on 9th July 2025.

-> Interested candidates had applied online from 13th March to 25th April 2025.

-> Candidates within the age of 25 years having specific education qualifications are eligible to apply for the exam.

-> The candidates must go through the Indian Army Havildar SAC Eligibility Criteria to know about the required qualification in detail. 

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