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Question

If 5.12 × 50625 × 0.5488 = $2^a3^b5^c7^d$, then find the value of a + b + c + d.

This question was previously asked in
RRB Group D 2024 Question Paper PDF (27-Dec-2025) (Shift 2)
The correct answer is

12

Correct Answer: 12

Prime factorisations:

  • 5.12 = 512/100 = 2⁹/(2²×5²) = 27/5²
  • 50625 = 225² = (3²×5²)² = 34×54
  • 0.5488 = 5488/10000 = (24×73)/(24×54) = 73/54

Product = 27/5² × 34×54 × 73/54

= 27 × 34 × 5(4−2−4) × 73

= 27 × 34 × 5−2 × 73

So a=7, b=4, c=−2, d=3

a+b+c+d = 7+4+(−2)+3 = 12

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