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Finding the Fourth Proportional to 100.35, 138.42 and 78.57

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Solution

The fourth proportional to 100.35, 138.42 and 78.57 is: 108.38

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.35 : 138.42 = 78.57 : x
  2. Step 2: Convert to fraction form
    100.35/138.42 = 78.57/x
  3. Step 3: Cross multiply
    100.35x = 138.42 × 78.57
  4. Step 4: Simplify right side
    100.35x = 10,875.66
  5. Step 5: Solve for x
    x = 10,875.66/100.35
  6. Step 6: Final answer
    x = 108.38

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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.