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Finding the Fourth Proportional to 918.70, 1,378.04 and 431.40

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Solution

The fourth proportional to 918.70, 1,378.04 and 431.40 is: 647.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    918.70 : 1,378.04 = 431.40 : x
  2. Step 2: Convert to fraction form
    918.70/1,378.04 = 431.40/x
  3. Step 3: Cross multiply
    918.70x = 1,378.04 × 431.40
  4. Step 4: Simplify right side
    918.70x = 594,486.46
  5. Step 5: Solve for x
    x = 594,486.46/918.70
  6. Step 6: Final answer
    x = 647.10

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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.