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Finding the Fourth Proportional to 61.68, 85.14 and 39.90

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Solution

The fourth proportional to 61.68, 85.14 and 39.90 is: 55.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    61.68 : 85.14 = 39.90 : x
  2. Step 2: Convert to fraction form
    61.68/85.14 = 39.90/x
  3. Step 3: Cross multiply
    61.68x = 85.14 × 39.90
  4. Step 4: Simplify right side
    61.68x = 3,397.09
  5. Step 5: Solve for x
    x = 3,397.09/61.68
  6. Step 6: Final answer
    x = 55.08

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.