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Finding the Third Proportional to 689.50 and 1,280

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Solution

The third proportional to 689.50 and 1,280 is: 2,376.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    689.50 : 1,280 = 1,280 : x
  2. Step 2: Convert to fraction form
    689.50/1,280 = 1,280/x
  3. Step 3: Cross multiply
    689.50x = 1,280 × 1,280
  4. Step 4: Simplify right side
    689.50x = 1,638,400
  5. Step 5: Solve for x
    x = 1,638,400/689.50
  6. Step 6: Final answer
    x = 2,376.21

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Why These Related Problems?

These problems maintain the same ratio (1.86) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.