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Finding the Fourth Proportional to 215.40, 297.21 and 128.06

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Solution

The fourth proportional to 215.40, 297.21 and 128.06 is: 176.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    215.40 : 297.21 = 128.06 : x
  2. Step 2: Convert to fraction form
    215.40/297.21 = 128.06/x
  3. Step 3: Cross multiply
    215.40x = 297.21 × 128.06
  4. Step 4: Simplify right side
    215.40x = 38,060.71
  5. Step 5: Solve for x
    x = 38,060.71/215.40
  6. Step 6: Final answer
    x = 176.70

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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.