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Finding the Fourth Proportional to 100.40, 138.55 and 65.45

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Solution

The fourth proportional to 100.40, 138.55 and 65.45 is: 90.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.40 : 138.55 = 65.45 : x
  2. Step 2: Convert to fraction form
    100.40/138.55 = 65.45/x
  3. Step 3: Cross multiply
    100.40x = 138.55 × 65.45
  4. Step 4: Simplify right side
    100.40x = 9,068.20
  5. Step 5: Solve for x
    x = 9,068.20/100.40
  6. Step 6: Final answer
    x = 90.32

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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.