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Finding the Fourth Proportional to 645.39, 890.69 and 396.65

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Solution

The fourth proportional to 645.39, 890.69 and 396.65 is: 547.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    645.39 : 890.69 = 396.65 : x
  2. Step 2: Convert to fraction form
    645.39/890.69 = 396.65/x
  3. Step 3: Cross multiply
    645.39x = 890.69 × 396.65
  4. Step 4: Simplify right side
    645.39x = 353,285.75
  5. Step 5: Solve for x
    x = 353,285.75/645.39
  6. Step 6: Final answer
    x = 547.40

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1.5x scale

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.