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Finding the Fourth Proportional to 138, 207 and 90.21

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Solution

The fourth proportional to 138, 207 and 90.21 is: 135.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    138 : 207 = 90.21 : x
  2. Step 2: Convert to fraction form
    138/207 = 90.21/x
  3. Step 3: Cross multiply
    138x = 207 × 90.21
  4. Step 4: Simplify right side
    138x = 18,673.47
  5. Step 5: Solve for x
    x = 18,673.47/138
  6. Step 6: Final answer
    x = 135.32

Related Problems

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Double scale
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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.