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Question

Solve the following. 

$\frac{(28.4)^2 - (24.4)^2}{(28.4 - 24.4)} = ?$

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
52.8

Algebraic Simplification Using Difference of Squares

The problem requires simplifying the expression $\frac{(28.4)^2 - (24.4)^2}{(28.4 - 24.4)}$. This can be solved efficiently using the algebraic identity for the difference of squares: $a^2 - b^2 = (a - b)(a + b)$.

Applying the Difference of Squares Formula

Let $a = 28.4$ and $b = 24.4$. Applying the formula to the numerator:

$(28.4)^2 - (24.4)^2 = (28.4 - 24.4)(28.4 + 24.4)$

Simplifying the Expression

Substitute the factored numerator back into the original expression:

$ \frac{(28.4 - 24.4)(28.4 + 24.4)}{(28.4 - 24.4)} $

The term $(28.4 - 24.4)$ appears in both the numerator and the denominator. We can cancel this term:

$ \frac{\cancel{(28.4 - 24.4)}(28.4 + 24.4)}{\cancel{(28.4 - 24.4)}} $

Final Calculation

The expression simplifies to:

$ 28.4 + 24.4 $

Performing the addition:

$ 28.4 + 24.4 = 52.8 $

Therefore, the value of the expression is 52.8.

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