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Finding the Fourth Proportional to 715.78, 987.72 and 405.28

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Solution

The fourth proportional to 715.78, 987.72 and 405.28 is: 559.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    715.78 : 987.72 = 405.28 : x
  2. Step 2: Convert to fraction form
    715.78/987.72 = 405.28/x
  3. Step 3: Cross multiply
    715.78x = 987.72 × 405.28
  4. Step 4: Simplify right side
    715.78x = 400,303.16
  5. Step 5: Solve for x
    x = 400,303.16/715.78
  6. Step 6: Final answer
    x = 559.25

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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.