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Finding the Fourth Proportional to 690.38, 1,040.74 and 644.55

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Solution

The fourth proportional to 690.38, 1,040.74 and 644.55 is: 971.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    690.38 : 1,040.74 = 644.55 : x
  2. Step 2: Convert to fraction form
    690.38/1,040.74 = 644.55/x
  3. Step 3: Cross multiply
    690.38x = 1,040.74 × 644.55
  4. Step 4: Simplify right side
    690.38x = 670,808.97
  5. Step 5: Solve for x
    x = 670,808.97/690.38
  6. Step 6: Final answer
    x = 971.65

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.