Explanation

Write the decimals as fractions: 0.064 = 64/1000, 6.25 = 625/100, 0.081 = 81/1000, 4.84 = 484/100. Then (0.064 × 6.25)/(0.081 × 4.84) = (64 × 625)/(81 × 484) = 40000/39204 = 10000/9801 = (100/99)². Taking the square root gives 100/99, which is option B. Options like 10/99 or 99 come from mishandling the decimal places or forgetting the square root.