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Finding the Fourth Proportional to 1,069.90, 1,605 and 420.56

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Solution

The fourth proportional to 1,069.90, 1,605 and 420.56 is: 630.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,069.90 : 1,605 = 420.56 : x
  2. Step 2: Convert to fraction form
    1,069.90/1,605 = 420.56/x
  3. Step 3: Cross multiply
    1,069.90x = 1,605 × 420.56
  4. Step 4: Simplify right side
    1,069.90x = 674,998.80
  5. Step 5: Solve for x
    x = 674,998.80/1,069.90
  6. Step 6: Final answer
    x = 630.90

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.