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Finding the Fourth Proportional to 660.78, 990 and 386.64

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Solution

The fourth proportional to 660.78, 990 and 386.64 is: 579.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    660.78 : 990 = 386.64 : x
  2. Step 2: Convert to fraction form
    660.78/990 = 386.64/x
  3. Step 3: Cross multiply
    660.78x = 990 × 386.64
  4. Step 4: Simplify right side
    660.78x = 382,773.60
  5. Step 5: Solve for x
    x = 382,773.60/660.78
  6. Step 6: Final answer
    x = 579.28

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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.