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Finding the Fourth Proportional to 128.76, 177.72 and 78.99

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Solution

The fourth proportional to 128.76, 177.72 and 78.99 is: 109.03

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.76 : 177.72 = 78.99 : x
  2. Step 2: Convert to fraction form
    128.76/177.72 = 78.99/x
  3. Step 3: Cross multiply
    128.76x = 177.72 × 78.99
  4. Step 4: Simplify right side
    128.76x = 14,038.10
  5. Step 5: Solve for x
    x = 14,038.10/128.76
  6. Step 6: Final answer
    x = 109.03

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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.