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Finding the Fourth Proportional to 99.90, 137.78 and 87.58

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Solution

The fourth proportional to 99.90, 137.78 and 87.58 is: 120.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    99.90 : 137.78 = 87.58 : x
  2. Step 2: Convert to fraction form
    99.90/137.78 = 87.58/x
  3. Step 3: Cross multiply
    99.90x = 137.78 × 87.58
  4. Step 4: Simplify right side
    99.90x = 12,066.77
  5. Step 5: Solve for x
    x = 12,066.77/99.90
  6. Step 6: Final answer
    x = 120.79

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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.