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Finding the Fourth Proportional to 128.48, 177.40 and 76.80

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Solution

The fourth proportional to 128.48, 177.40 and 76.80 is: 106.04

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.48 : 177.40 = 76.80 : x
  2. Step 2: Convert to fraction form
    128.48/177.40 = 76.80/x
  3. Step 3: Cross multiply
    128.48x = 177.40 × 76.80
  4. Step 4: Simplify right side
    128.48x = 13,624.32
  5. Step 5: Solve for x
    x = 13,624.32/128.48
  6. Step 6: Final answer
    x = 106.04

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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.