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Finding the Fourth Proportional to 715.70, 987.78 and 405.20

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Solution

The fourth proportional to 715.70, 987.78 and 405.20 is: 559.24

Step by Step Solution

  1. Step 1: Write the proportion equation
    715.70 : 987.78 = 405.20 : x
  2. Step 2: Convert to fraction form
    715.70/987.78 = 405.20/x
  3. Step 3: Cross multiply
    715.70x = 987.78 × 405.20
  4. Step 4: Simplify right side
    715.70x = 400,243.52
  5. Step 5: Solve for x
    x = 400,243.52/715.70
  6. Step 6: Final answer
    x = 559.24

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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.