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Finding the Fourth Proportional to 720.90, 1,081.70 and 428.98

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Solution

The fourth proportional to 720.90, 1,081.70 and 428.98 is: 643.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    720.90 : 1,081.70 = 428.98 : x
  2. Step 2: Convert to fraction form
    720.90/1,081.70 = 428.98/x
  3. Step 3: Cross multiply
    720.90x = 1,081.70 × 428.98
  4. Step 4: Simplify right side
    720.90x = 464,025.25
  5. Step 5: Solve for x
    x = 464,025.25/720.90
  6. Step 6: Final answer
    x = 643.67

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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.