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Finding the Fourth Proportional to 621, 856.65 and 489.78

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Solution

The fourth proportional to 621, 856.65 and 489.78 is: 675.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    621 : 856.65 = 489.78 : x
  2. Step 2: Convert to fraction form
    621/856.65 = 489.78/x
  3. Step 3: Cross multiply
    621x = 856.65 × 489.78
  4. Step 4: Simplify right side
    621x = 419,570.04
  5. Step 5: Solve for x
    x = 419,570.04/621
  6. Step 6: Final answer
    x = 675.64

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.