Ratio, Proportion, Indices, LogarithmMCQPYQ Sep 24Question 894 of 305
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What is the value of (xbxc)(b+ca)×(xcxa)(c+ab)×(xaxb)(a+bc)\displaystyle \left(\frac{x^b}{x^c}\right)^{(b+c-a)} \times \left(\frac{x^c}{x^a}\right)^{(c+a-b)} \times \left(\frac{x^a}{x^b}\right)^{(a+b-c)}

Options

Ax(a+b+c)\displaystyle x^{(a+b+c)}
Bxabc\displaystyle x^{abc}
C-1
D1
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Correct Answer

Option d1

All Options:

  • Ax(a+b+c)\displaystyle x^{(a+b+c)}
  • Bxabc\displaystyle x^{abc}
  • C-1
  • D1

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Detailed Solution & Explanation

We want to simplify the expression:
(xbxc)b+ca×(xcxa)c+ab×(xaxb)a+bc\left(\frac{x^b}{x^c}\right)^{b+c-a} \times \left(\frac{x^c}{x^a}\right)^{c+a-b} \times \left(\frac{x^a}{x^b}\right)^{a+b-c}
Let us simplify each factor using exponent laws (xmxn=xmn\displaystyle \frac{x^m}{x^n} = x^{m-n} and (xm)n=xmn\displaystyle (x^m)^n = x^{mn}):
1. **First factor:**
(xbc)b+ca=x(bc)(b+ca)=xb2c2ab+ac\left(x^{b-c}\right)^{b+c-a} = x^{(b-c)(b+c-a)} = x^{b^2 - c^2 - ab + ac}
2. **Second factor:**
(xca)c+ab=x(ca)(c+ab)=xc2a2bc+ab\left(x^{c-a}\right)^{c+a-b} = x^{(c-a)(c+a-b)} = x^{c^2 - a^2 - bc + ab}
3. **Third factor:**
(xab)a+bc=x(ab)(a+bc)=xa2b2ac+bc\left(x^{a-b}\right)^{a+b-c} = x^{(a-b)(a+b-c)} = x^{a^2 - b^2 - ac + bc}

Now, multiply the three factors by adding their exponents (xmxn=xm+n\displaystyle x^m \cdot x^n = x^{m+n}):
Product=x(b2c2ab+ac)+(c2a2bc+ab)+(a2b2ac+bc)\text{Product} = x^{(b^2 - c^2 - ab + ac) + (c^2 - a^2 - bc + ab) + (a^2 - b^2 - ac + bc)}
Let us combine and simplify the exponent terms:
(b2b2)+(c2c2)+(a2a2)+(abab)+(bcbc)+(acac)=0(b^2 - b^2) + (c^2 - c^2) + (a^2 - a^2) + (ab - ab) + (bc - bc) + (ac - ac) = 0
Thus, the expression simplifies to:
x0=1x^0 = 1
This matches **Option D**.
Note: The textbook answer key incorrectly specifies **Option A** (x(a+b+c)\displaystyle x^{(a+b+c)}) as correct. However, our rigorous mathematical simplification clearly proves that all exponents cancel out to zero, yielding exactly 1\displaystyle 1 (Option D).
Hence, **Option D** is the correct answer.

About This Chapter: Ratio, Proportion, Indices, Logarithm

Paper

Paper 3: Quantitative Aptitude

Weightage

5-7 Marks

Key Topics

Ratio, Proportion, Indices, Logarithms

This chapter covers Ratio, Proportion, Indices, Logarithms and is part of Paper 3: Quantitative Aptitude in the CA Foundation exam.

View Official ICAI Syllabus

Exam Strategy Tip

This topic carries 5-7 Marks weightage. Focus on understanding core concepts rather than memorizing.

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