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Finding the Fourth Proportional to 811.70, 1,216.65 and 421.55

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Solution

The fourth proportional to 811.70, 1,216.65 and 421.55 is: 631.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    811.70 : 1,216.65 = 421.55 : x
  2. Step 2: Convert to fraction form
    811.70/1,216.65 = 421.55/x
  3. Step 3: Cross multiply
    811.70x = 1,216.65 × 421.55
  4. Step 4: Simplify right side
    811.70x = 512,878.81
  5. Step 5: Solve for x
    x = 512,878.81/811.70
  6. Step 6: Final answer
    x = 631.86

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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.