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Finding the Fourth Proportional to 921.90, 1,272.20 and 528.90

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Solution

The fourth proportional to 921.90, 1,272.20 and 528.90 is: 729.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    921.90 : 1,272.20 = 528.90 : x
  2. Step 2: Convert to fraction form
    921.90/1,272.20 = 528.90/x
  3. Step 3: Cross multiply
    921.90x = 1,272.20 × 528.90
  4. Step 4: Simplify right side
    921.90x = 672,866.58
  5. Step 5: Solve for x
    x = 672,866.58/921.90
  6. Step 6: Final answer
    x = 729.87

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.