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Finding the Fourth Proportional to 715.45, 987.45 and 420.70

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Solution

The fourth proportional to 715.45, 987.45 and 420.70 is: 580.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    715.45 : 987.45 = 420.70 : x
  2. Step 2: Convert to fraction form
    715.45/987.45 = 420.70/x
  3. Step 3: Cross multiply
    715.45x = 987.45 × 420.70
  4. Step 4: Simplify right side
    715.45x = 415,420.22
  5. Step 5: Solve for x
    x = 415,420.22/715.45
  6. Step 6: Final answer
    x = 580.64

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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.