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Finding the Third Proportional to 390 and 811.50

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Solution

The third proportional to 390 and 811.50 is: 1,688.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    390 : 811.50 = 811.50 : x
  2. Step 2: Convert to fraction form
    390/811.50 = 811.50/x
  3. Step 3: Cross multiply
    390x = 811.50 × 811.50
  4. Step 4: Simplify right side
    390x = 658,532.25
  5. Step 5: Solve for x
    x = 658,532.25/390
  6. Step 6: Final answer
    x = 1,688.54

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Why These Related Problems?

These problems maintain the same ratio (2.08) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.