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Finding the Fourth Proportional to 428.90, 642.90 and 212.36

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Solution

The fourth proportional to 428.90, 642.90 and 212.36 is: 318.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.90 : 642.90 = 212.36 : x
  2. Step 2: Convert to fraction form
    428.90/642.90 = 212.36/x
  3. Step 3: Cross multiply
    428.90x = 642.90 × 212.36
  4. Step 4: Simplify right side
    428.90x = 136,526.24
  5. Step 5: Solve for x
    x = 136,526.24/428.90
  6. Step 6: Final answer
    x = 318.32

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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.