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Finding the Fourth Proportional to 813.60, 1,213.20 and 781.20

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Solution

The fourth proportional to 813.60, 1,213.20 and 781.20 is: 1,164.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    813.60 : 1,213.20 = 781.20 : x
  2. Step 2: Convert to fraction form
    813.60/1,213.20 = 781.20/x
  3. Step 3: Cross multiply
    813.60x = 1,213.20 × 781.20
  4. Step 4: Simplify right side
    813.60x = 947,751.84
  5. Step 5: Solve for x
    x = 947,751.84/813.60
  6. Step 6: Final answer
    x = 1,164.89

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.