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Finding the Fourth Proportional to 715.60, 987.56 and 420.85

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Solution

The fourth proportional to 715.60, 987.56 and 420.85 is: 580.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    715.60 : 987.56 = 420.85 : x
  2. Step 2: Convert to fraction form
    715.60/987.56 = 420.85/x
  3. Step 3: Cross multiply
    715.60x = 987.56 × 420.85
  4. Step 4: Simplify right side
    715.60x = 415,614.63
  5. Step 5: Solve for x
    x = 415,614.63/715.60
  6. Step 6: Final answer
    x = 580.79

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1.5x scale

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.