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Finding the Fourth Proportional to 811.59, 1,215.78 and 421.84

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Solution

The fourth proportional to 811.59, 1,215.78 and 421.84 is: 631.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    811.59 : 1,215.78 = 421.84 : x
  2. Step 2: Convert to fraction form
    811.59/1,215.78 = 421.84/x
  3. Step 3: Cross multiply
    811.59x = 1,215.78 × 421.84
  4. Step 4: Simplify right side
    811.59x = 512,866.95
  5. Step 5: Solve for x
    x = 512,866.95/811.59
  6. Step 6: Final answer
    x = 631.93

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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.