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Finding the Fourth Proportional to 128.40, 177.16 and 76.64

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Solution

The fourth proportional to 128.40, 177.16 and 76.64 is: 105.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.40 : 177.16 = 76.64 : x
  2. Step 2: Convert to fraction form
    128.40/177.16 = 76.64/x
  3. Step 3: Cross multiply
    128.40x = 177.16 × 76.64
  4. Step 4: Simplify right side
    128.40x = 13,577.54
  5. Step 5: Solve for x
    x = 13,577.54/128.40
  6. Step 6: Final answer
    x = 105.74

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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.