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Finding the Fourth Proportional to 715.53, 987.12 and 420.78

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Solution

The fourth proportional to 715.53, 987.12 and 420.78 is: 580.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    715.53 : 987.12 = 420.78 : x
  2. Step 2: Convert to fraction form
    715.53/987.12 = 420.78/x
  3. Step 3: Cross multiply
    715.53x = 987.12 × 420.78
  4. Step 4: Simplify right side
    715.53x = 415,360.35
  5. Step 5: Solve for x
    x = 415,360.35/715.53
  6. Step 6: Final answer
    x = 580.49

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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.