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Finding the Fourth Proportional to 64.80, 89.38 and 39.89

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Solution

The fourth proportional to 64.80, 89.38 and 39.89 is: 55.02

Step by Step Solution

  1. Step 1: Write the proportion equation
    64.80 : 89.38 = 39.89 : x
  2. Step 2: Convert to fraction form
    64.80/89.38 = 39.89/x
  3. Step 3: Cross multiply
    64.80x = 89.38 × 39.89
  4. Step 4: Simplify right side
    64.80x = 3,565.37
  5. Step 5: Solve for x
    x = 3,565.37/64.80
  6. Step 6: Final answer
    x = 55.02

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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.