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Finding the Third Proportional to 390 and 842

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Solution

The third proportional to 390 and 842 is: 1,817.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    390 : 842 = 842 : x
  2. Step 2: Convert to fraction form
    390/842 = 842/x
  3. Step 3: Cross multiply
    390x = 842 × 842
  4. Step 4: Simplify right side
    390x = 708,964
  5. Step 5: Solve for x
    x = 708,964/390
  6. Step 6: Final answer
    x = 1,817.86

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These problems maintain the same ratio (2.16) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.