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Finding the Fourth Proportional to 921.15, 1,381.55 and 420.89

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Solution

The fourth proportional to 921.15, 1,381.55 and 420.89 is: 631.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    921.15 : 1,381.55 = 420.89 : x
  2. Step 2: Convert to fraction form
    921.15/1,381.55 = 420.89/x
  3. Step 3: Cross multiply
    921.15x = 1,381.55 × 420.89
  4. Step 4: Simplify right side
    921.15x = 581,471.57
  5. Step 5: Solve for x
    x = 581,471.57/921.15
  6. Step 6: Final answer
    x = 631.25

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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.