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Finding the Fourth Proportional to 66.40, 90.40 and 65.80

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Solution

The fourth proportional to 66.40, 90.40 and 65.80 is: 89.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    66.40 : 90.40 = 65.80 : x
  2. Step 2: Convert to fraction form
    66.40/90.40 = 65.80/x
  3. Step 3: Cross multiply
    66.40x = 90.40 × 65.80
  4. Step 4: Simplify right side
    66.40x = 5,948.32
  5. Step 5: Solve for x
    x = 5,948.32/66.40
  6. Step 6: Final answer
    x = 89.58

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Why These Related Problems?

These problems maintain the same ratio (1.36) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.