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Finding the Fourth Proportional to 921.36, 1,381.86 and 420.91

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Solution

The fourth proportional to 921.36, 1,381.86 and 420.91 is: 631.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    921.36 : 1,381.86 = 420.91 : x
  2. Step 2: Convert to fraction form
    921.36/1,381.86 = 420.91/x
  3. Step 3: Cross multiply
    921.36x = 1,381.86 × 420.91
  4. Step 4: Simplify right side
    921.36x = 581,635.26
  5. Step 5: Solve for x
    x = 581,635.26/921.36
  6. Step 6: Final answer
    x = 631.28

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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.