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Finding the Fourth Proportional to 215.21, 322.47 and 128.40

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Solution

The fourth proportional to 215.21, 322.47 and 128.40 is: 192.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    215.21 : 322.47 = 128.40 : x
  2. Step 2: Convert to fraction form
    215.21/322.47 = 128.40/x
  3. Step 3: Cross multiply
    215.21x = 322.47 × 128.40
  4. Step 4: Simplify right side
    215.21x = 41,405.15
  5. Step 5: Solve for x
    x = 41,405.15/215.21
  6. Step 6: Final answer
    x = 192.40

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.