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Finding the Fourth Proportional to 661.17, 990.62 and 429.78

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Solution

The fourth proportional to 661.17, 990.62 and 429.78 is: 643.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    661.17 : 990.62 = 429.78 : x
  2. Step 2: Convert to fraction form
    661.17/990.62 = 429.78/x
  3. Step 3: Cross multiply
    661.17x = 990.62 × 429.78
  4. Step 4: Simplify right side
    661.17x = 425,748.66
  5. Step 5: Solve for x
    x = 425,748.66/661.17
  6. Step 6: Final answer
    x = 643.93

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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.