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Finding the Fourth Proportional to 811.67, 1,216.79 and 421.45

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Solution

The fourth proportional to 811.67, 1,216.79 and 421.45 is: 631.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    811.67 : 1,216.79 = 421.45 : x
  2. Step 2: Convert to fraction form
    811.67/1,216.79 = 421.45/x
  3. Step 3: Cross multiply
    811.67x = 1,216.79 × 421.45
  4. Step 4: Simplify right side
    811.67x = 512,811.00
  5. Step 5: Solve for x
    x = 512,811.00/811.67
  6. Step 6: Final answer
    x = 631.80

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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.