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Finding the Fourth Proportional to 659.76, 990 and 428.58

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Solution

The fourth proportional to 659.76, 990 and 428.58 is: 643.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    659.76 : 990 = 428.58 : x
  2. Step 2: Convert to fraction form
    659.76/990 = 428.58/x
  3. Step 3: Cross multiply
    659.76x = 990 × 428.58
  4. Step 4: Simplify right side
    659.76x = 424,294.20
  5. Step 5: Solve for x
    x = 424,294.20/659.76
  6. Step 6: Final answer
    x = 643.10

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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.