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Finding the Fourth Proportional to 811.80, 1,217.70 and 771.30

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Solution

The fourth proportional to 811.80, 1,217.70 and 771.30 is: 1,156.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    811.80 : 1,217.70 = 771.30 : x
  2. Step 2: Convert to fraction form
    811.80/1,217.70 = 771.30/x
  3. Step 3: Cross multiply
    811.80x = 1,217.70 × 771.30
  4. Step 4: Simplify right side
    811.80x = 939,212.01
  5. Step 5: Solve for x
    x = 939,212.01/811.80
  6. Step 6: Final answer
    x = 1,156.95

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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.