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Finding the Fourth Proportional to 100.53, 138.63 and 78.66

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Solution

The fourth proportional to 100.53, 138.63 and 78.66 is: 108.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.53 : 138.63 = 78.66 : x
  2. Step 2: Convert to fraction form
    100.53/138.63 = 78.66/x
  3. Step 3: Cross multiply
    100.53x = 138.63 × 78.66
  4. Step 4: Simplify right side
    100.53x = 10,904.64
  5. Step 5: Solve for x
    x = 10,904.64/100.53
  6. Step 6: Final answer
    x = 108.47

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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.