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Finding the Fourth Proportional to 715.80, 987.80 and 405.28

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Solution

The fourth proportional to 715.80, 987.80 and 405.28 is: 559.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    715.80 : 987.80 = 405.28 : x
  2. Step 2: Convert to fraction form
    715.80/987.80 = 405.28/x
  3. Step 3: Cross multiply
    715.80x = 987.80 × 405.28
  4. Step 4: Simplify right side
    715.80x = 400,335.58
  5. Step 5: Solve for x
    x = 400,335.58/715.80
  6. Step 6: Final answer
    x = 559.28

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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.