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Question

(0.1 × 0.1 × 0.1 + 0.04 × 0.04 × 0.04) ÷ (0.2 × 0.2 × 0.2 + 0.08 × 0.08 × 0.08) = ______.

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is

0.125

Solving the Decimal Expression

Let's solve the given mathematical expression step by step. The expression is:

\((0.1 \times 0.1 \times 0.1 + 0.04 \times 0.04 \times 0.04) \div (0.2 \times 0.2 \times 0.2 + 0.08 \times 0.08 \times 0.08)\)

We can rewrite the terms using exponents:

\((0.1^3 + 0.04^3) \div (0.2^3 + 0.08^3)\)

Let's look at the terms in the denominator and compare them to the terms in the numerator:

  • \(0.2 = 2 \times 0.1\)
  • \(0.08 = 2 \times 0.04\)

Now substitute these into the denominator:

\((2 \times 0.1)^3 + (2 \times 0.04)^3\)

Using the exponent rule \((ab)^n = a^n b^n\), we can write:

\(2^3 \times 0.1^3 + 2^3 \times 0.04^3\)

We can factor out \(2^3\) from both terms in the denominator:

\(2^3 (0.1^3 + 0.04^3)\)

Since \(2^3 = 2 \times 2 \times 2 = 8\), the denominator is:

\(8 (0.1^3 + 0.04^3)\)

Now substitute this back into the original expression:

\(\frac{0.1^3 + 0.04^3}{8 (0.1^3 + 0.04^3)}\)

We can see that the term \((0.1^3 + 0.04^3)\) appears in both the numerator and the denominator. As \(0.1^3 = 0.001\) and \(0.04^3 = 0.000064\), their sum is \(0.001064\), which is not zero. Therefore, we can cancel out this common term:

\(\frac{\cancel{(0.1^3 + 0.04^3)}}{8 \cancel{(0.1^3 + 0.04^3)}}\)

This simplifies the expression to:

\(\frac{1}{8}\)

Finally, convert the fraction \(\frac{1}{8}\) to a decimal:

\(1 \div 8 = 0.125\)

So, the value of the expression is 0.125.

Revision Table: Key Calculation Steps

Step Calculation Result
Numerator terms \(0.1^3\) \(0.001\)
Numerator terms \(0.04^3\) \(0.000064\)
Denominator term relationship \(0.2 = 2 \times 0.1\) -
Denominator term relationship \(0.08 = 2 \times 0.04\) -
Denominator using relationship \((2 \times 0.1)^3 + (2 \times 0.04)^3\) \(2^3(0.1^3 + 0.04^3)\)
Simplify fraction \(\frac{0.1^3 + 0.04^3}{8 (0.1^3 + 0.04^3)}\) \(\frac{1}{8}\)
Convert to decimal \(\frac{1}{8}\) \(0.125\)

Additional Information: Properties of Exponents and Decimals

This problem utilizes basic arithmetic operations with decimals and properties of exponents. Understanding these concepts is crucial for solving such expressions.

  • Exponents: An exponent indicates how many times a base number is multiplied by itself. For example, \(a^3 = a \times a \times a\).
  • Property \((ab)^n = a^n b^n\): When a product of numbers is raised to a power, you can raise each number in the product to that power separately and then multiply the results. This property was key to simplifying the denominator in the problem.
  • Decimal Arithmetic: Performing multiplication and division with decimals requires careful handling of the decimal point. Converting fractions like \(\frac{1}{8}\) to decimals involves dividing the numerator by the denominator. \(\frac{1}{8}\) is a common fraction equivalent to 0.125.

Breaking down complex expressions into simpler parts and identifying relationships between terms can make solving them much easier.

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