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Finding the Third Proportional to 390 and 858

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Solution

The third proportional to 390 and 858 is: 1,887.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    390 : 858 = 858 : x
  2. Step 2: Convert to fraction form
    390/858 = 858/x
  3. Step 3: Cross multiply
    390x = 858 × 858
  4. Step 4: Simplify right side
    390x = 736,164
  5. Step 5: Solve for x
    x = 736,164/390
  6. Step 6: Final answer
    x = 1,887.60

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These problems maintain the same ratio (2.20) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.