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Finding the Fourth Proportional to 715.64, 987.60 and 405.20

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Solution

The fourth proportional to 715.64, 987.60 and 405.20 is: 559.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    715.64 : 987.60 = 405.20 : x
  2. Step 2: Convert to fraction form
    715.64/987.60 = 405.20/x
  3. Step 3: Cross multiply
    715.64x = 987.60 × 405.20
  4. Step 4: Simplify right side
    715.64x = 400,175.52
  5. Step 5: Solve for x
    x = 400,175.52/715.64
  6. Step 6: Final answer
    x = 559.19

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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.