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Finding the Fourth Proportional to 100.63, 138.76 and 90.80

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Solution

The fourth proportional to 100.63, 138.76 and 90.80 is: 125.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.63 : 138.76 = 90.80 : x
  2. Step 2: Convert to fraction form
    100.63/138.76 = 90.80/x
  3. Step 3: Cross multiply
    100.63x = 138.76 × 90.80
  4. Step 4: Simplify right side
    100.63x = 12,599.41
  5. Step 5: Solve for x
    x = 12,599.41/100.63
  6. Step 6: Final answer
    x = 125.21

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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.