EquationsMCQPYQ Sep 24Question 1013 of 221
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A number consist of two digits. The digits in the ten's place is 3 times the digit in the unit's place. If 54 is subtracted from the number, then the digits are reversed. The number is:

Chapter 2 Diagram

Options

A62
B39
C93
D31
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Correct Answer

Option c93

All Options:

  • A62
  • B39
  • C93
  • D31

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Detailed Solution & Explanation

Let the digit in the ten's place be x\displaystyle x and the digit in the unit's place be y\displaystyle y.
According to the first condition:
x=3y— (Equation 1)x = 3y \quad \text{--- (Equation 1)}
The value of the original two-digit number is 10x+y\displaystyle 10x + y.
If 54 is subtracted from this number, the digits are reversed, making the value of the new number 10y+x\displaystyle 10y + x.
According to the second condition:
(10x+y)54=10y+x(10x + y) - 54 = 10y + x
10xx+y10y=5410x - x + y - 10y = 54
9x9y=549x - 9y = 54
xy=6— (Equation 2)x - y = 6 \quad \text{--- (Equation 2)}
Substitute Equation 1 (x=3y\displaystyle x = 3y) into Equation 2:
3yy=63y - y = 6
2y=6    y=32y = 6 \implies y = 3
Now, find x\displaystyle x:
x=3(3)=9x = 3(3) = 9
Therefore, the original number is:
10x+y=10(9)+3=9310x + y = 10(9) + 3 = 93
**Correct Option: (c)**

About This Chapter: Equations

Paper

Paper 3: Quantitative Aptitude

Weightage

4-6 Marks

Key Topics

Linear, Quadratic and Cubic Equations

This chapter covers Linear, Quadratic and Cubic Equations and is part of Paper 3: Quantitative Aptitude in the CA Foundation exam.

View Official ICAI Syllabus

Exam Strategy Tip

This topic carries 4-6 Marks weightage. Focus on understanding core concepts rather than memorizing.

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