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Question

What is the LCM of 3.6, 0.009, 0.27 ?

This question was previously asked in
CDS 1 2026 Maths Question Paper (12-Apr-2026)
The correct answer is

10.8

Convert Numbers to Fractions

First, represent the given decimal numbers 3.6, 0.009, and 0.27 as fractions. To do this, place the number without the decimal point over the appropriate power of 10.

  • \(3.6 = \frac{36}{10}\)
  • \(0.009 = \frac{9}{1000}\)
  • \(0.27 = \frac{27}{100}\)

Find LCM of Numerators

Next, calculate the Least Common Multiple (LCM) of the numerators of these fractions: 36, 9, and 27.

Use prime factorization for each numerator:

  • \(36 = 2^2 \times 3^2\)
  • \(9 = 3^2\)
  • \(27 = 3^3\)

The LCM is found by taking the highest power of each prime factor present in any of the numbers: \(LCM(36, 9, 27) = 2^2 \times 3^3 = 4 \times 27 = 108\).

Find GCD of Denominators

Then, calculate the Greatest Common Divisor (GCD) of the denominators: 10, 1000, and 100.

Use prime factorization for each denominator:

  • \(10 = 2^1 \times 5^1\)
  • \(1000 = 10^3 = (2 \times 5)^3 = 2^3 \times 5^3\)
  • \(100 = 10^2 = (2 \times 5)^2 = 2^2 \times 5^2\)

The GCD is found by taking the lowest power of each prime factor common to all the numbers: \(GCD(10, 1000, 100) = 2^1 \times 5^1 = 10\).

Compute LCM of Decimal Numbers

The formula for the LCM of fractions \(\frac{a}{b}, \frac{c}{d}, \frac{e}{f}\) is \(\frac{LCM(a, c, e)}{GCD(b, d, f)}\). Apply this formula to find the LCM of the original decimal numbers.

\(LCM(3.6, 0.009, 0.27) = \frac{LCM(\text{Numerators})}{\text{GCD}(\text{Denominators})} = \frac{108}{10}\)

\(LCM = 10.8\).

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Important Questions from LCM and HCF

  1. The greatest three-digit number which is divisible by 14, 28, and 42 is:

  2. What is the greatest number that will divide 209 and 347 leaving remainder 5 and 7 respectively?

  3. A number is three times another number and their HCF is 8. What is the sum of the squares of the numbers?

  4. The HCF of 2091, 3485 and 4879 is x. The sum of the digits of x is:

  5. If three numbers are in ratio of 3 : 5 : 7 and their LCM is 2415, what is the difference between the second number and the first number?

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