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Finding the Fourth Proportional to 812.19, 1,217.90 and 421.80

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Solution

The fourth proportional to 812.19, 1,217.90 and 421.80 is: 632.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    812.19 : 1,217.90 = 421.80 : x
  2. Step 2: Convert to fraction form
    812.19/1,217.90 = 421.80/x
  3. Step 3: Cross multiply
    812.19x = 1,217.90 × 421.80
  4. Step 4: Simplify right side
    812.19x = 513,703.54
  5. Step 5: Solve for x
    x = 513,703.54/812.19
  6. Step 6: Final answer
    x = 632.49

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1.5x scale

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.