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Finding the Fourth Proportional to 485.90, 670.40 and 289.40

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Solution

The fourth proportional to 485.90, 670.40 and 289.40 is: 399.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    485.90 : 670.40 = 289.40 : x
  2. Step 2: Convert to fraction form
    485.90/670.40 = 289.40/x
  3. Step 3: Cross multiply
    485.90x = 670.40 × 289.40
  4. Step 4: Simplify right side
    485.90x = 194,013.76
  5. Step 5: Solve for x
    x = 194,013.76/485.90
  6. Step 6: Final answer
    x = 399.29

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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.