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Finding the Fourth Proportional to 978.05, 1,349.78 and 645.90

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Solution

The fourth proportional to 978.05, 1,349.78 and 645.90 is: 891.38

Step by Step Solution

  1. Step 1: Write the proportion equation
    978.05 : 1,349.78 = 645.90 : x
  2. Step 2: Convert to fraction form
    978.05/1,349.78 = 645.90/x
  3. Step 3: Cross multiply
    978.05x = 1,349.78 × 645.90
  4. Step 4: Simplify right side
    978.05x = 871,814.61
  5. Step 5: Solve for x
    x = 871,814.61/978.05
  6. Step 6: Final answer
    x = 891.38

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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.