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Finding the Fourth Proportional to 678.84, 1,018.76 and 386.40

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Solution

The fourth proportional to 678.84, 1,018.76 and 386.40 is: 579.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    678.84 : 1,018.76 = 386.40 : x
  2. Step 2: Convert to fraction form
    678.84/1,018.76 = 386.40/x
  3. Step 3: Cross multiply
    678.84x = 1,018.76 × 386.40
  4. Step 4: Simplify right side
    678.84x = 393,648.86
  5. Step 5: Solve for x
    x = 393,648.86/678.84
  6. Step 6: Final answer
    x = 579.88

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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.