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The value of \(\dfrac{(2.3)^3 + (1.5)^3 + (1.2)^3 - 3 \times 2.3 \times 1.5 \times 1.2}{(2.3)^2 + (1.5)^2 + (1.2)^2 - 2.3 \times 1.5 - 1.5 \times 1.2 - 1.2 \times 2.3}\) is equal to:

This question was previously asked in
RRB NTPC 2025 Graduate CBT 2 Question Paper PDF (10-Jul-2026) (Shift 1)
The correct answer is

5

Recall the algebraic identity: \(a^3 + b^3 + c^3 - 3abc = (a + b + c)(a^2 + b^2 + c^2 - ab - bc - ca)\).

The given expression is exactly in this form with \(a = 2.3\), \(b = 1.5\), \(c = 1.2\).

Dividing numerator by denominator cancels \((a^2 + b^2 + c^2 - ab - bc - ca)\), leaving simply \(a + b + c\).

Calculate: \(a + b + c = 2.3 + 1.5 + 1.2 = 5.0\).

Hence, the value of the expression is 5.

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Similar Questions

  1. If $a + b + c = 10$ and $ab + bc + ca = 31$, find the value of $a^2 + b^2 + c^2$
  2. If $a + b + c = 0$, then find the value of $\frac{(a^2+b^2+c^2)^2}{a^2b^2+b^2c^2+c^2a^2}$

  3. If $x^4 + \frac{1}{x^4} = 322$, then $x^3 - \frac{1}{x^3} = ?$
  4. If $(x + \frac{1}{x}) = 7$, then $(x - \frac{1}{x})$ is equal to:
  5. If $x + y + z = 0$, then the value of $\frac{x^2}{yz} + \frac{y^2}{zx} + \frac{z^2}{xy}$ is:
  6. What is the value of the following expression:

    $(1 + x)(1 + x^2)(1 + x^4)(1 + x^8)(1 - x)$
  7. If $a + b + c = 17$, $abc = 168$, and $ab + bc + ca = 94$, then $a^3 + b^3 + c^3 = ?$
  8. If $a = \frac{b^2}{b - a}$, then the value of $a^3 + b^3$ is:
  9. If $ab = 10$ and $a^{2} + b^{2} = 29$, then $(a - b)^{2} = ?$
  10. Find the value of $\frac{(74 + 47)^2 + (74 - 47)^2}{74^2 + 47^2}$

Important Questions from Identities

  1. If \(2x + { {1} \over 3x}= 5, x ≠ 0\) , then what is the value of  \(27x^3+{{1} \over 8x^3}\) ?

  2. If x 2 + 4y 2 = 40, xy = 6 and x > 2y then the value of x - 2y is:

  3. \(\dfrac{(0.73)^3+(0.31)^3}{(0.73)^2-0.73\times0.31+(0.31)^2}\)
  4. \(\dfrac{(5.17-2.19)^2-(5.17+2.19)^2}{11.3223}\)
  5. If a(a + b + c) 2= 1792; b(a + b + c) 2= 1536; c(a + b + c) 2= 768 then what will be the value of a?

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