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Finding the Fourth Proportional to 813.09, 1,220 and 428.25

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Solution

The fourth proportional to 813.09, 1,220 and 428.25 is: 642.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    813.09 : 1,220 = 428.25 : x
  2. Step 2: Convert to fraction form
    813.09/1,220 = 428.25/x
  3. Step 3: Cross multiply
    813.09x = 1,220 × 428.25
  4. Step 4: Simplify right side
    813.09x = 522,465
  5. Step 5: Solve for x
    x = 522,465/813.09
  6. Step 6: Final answer
    x = 642.57

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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.