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Finding the Fourth Proportional to 100.80, 139.09 and 61.45

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Solution

The fourth proportional to 100.80, 139.09 and 61.45 is: 84.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.80 : 139.09 = 61.45 : x
  2. Step 2: Convert to fraction form
    100.80/139.09 = 61.45/x
  3. Step 3: Cross multiply
    100.80x = 139.09 × 61.45
  4. Step 4: Simplify right side
    100.80x = 8,547.08
  5. Step 5: Solve for x
    x = 8,547.08/100.80
  6. Step 6: Final answer
    x = 84.79

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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.