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Finding the Fourth Proportional to 986.40, 1,478.64 and 408.72

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Solution

The fourth proportional to 986.40, 1,478.64 and 408.72 is: 612.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    986.40 : 1,478.64 = 408.72 : x
  2. Step 2: Convert to fraction form
    986.40/1,478.64 = 408.72/x
  3. Step 3: Cross multiply
    986.40x = 1,478.64 × 408.72
  4. Step 4: Simplify right side
    986.40x = 604,349.74
  5. Step 5: Solve for x
    x = 604,349.74/986.40
  6. Step 6: Final answer
    x = 612.68

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.