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Finding the Fourth Proportional to 690.78, 1,035.90 and 430.40

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Solution

The fourth proportional to 690.78, 1,035.90 and 430.40 is: 645.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    690.78 : 1,035.90 = 430.40 : x
  2. Step 2: Convert to fraction form
    690.78/1,035.90 = 430.40/x
  3. Step 3: Cross multiply
    690.78x = 1,035.90 × 430.40
  4. Step 4: Simplify right side
    690.78x = 445,851.36
  5. Step 5: Solve for x
    x = 445,851.36/690.78
  6. Step 6: Final answer
    x = 645.43

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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.