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Finding the Third Proportional to 428.75 and 690.25

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Solution

The third proportional to 428.75 and 690.25 is: 1,111.24

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.75 : 690.25 = 690.25 : x
  2. Step 2: Convert to fraction form
    428.75/690.25 = 690.25/x
  3. Step 3: Cross multiply
    428.75x = 690.25 × 690.25
  4. Step 4: Simplify right side
    428.75x = 476,445.06
  5. Step 5: Solve for x
    x = 476,445.06/428.75
  6. Step 6: Final answer
    x = 1,111.24

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Why These Related Problems?

These problems maintain the same ratio (1.61) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.