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Finding the Fourth Proportional to 813.80, 1,221.90 and 631.40

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Solution

The fourth proportional to 813.80, 1,221.90 and 631.40 is: 948.03

Step by Step Solution

  1. Step 1: Write the proportion equation
    813.80 : 1,221.90 = 631.40 : x
  2. Step 2: Convert to fraction form
    813.80/1,221.90 = 631.40/x
  3. Step 3: Cross multiply
    813.80x = 1,221.90 × 631.40
  4. Step 4: Simplify right side
    813.80x = 771,507.66
  5. Step 5: Solve for x
    x = 771,507.66/813.80
  6. Step 6: Final answer
    x = 948.03

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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.