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Finding the Fourth Proportional to 638.78, 881.57 and 386.78

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Solution

The fourth proportional to 638.78, 881.57 and 386.78 is: 533.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    638.78 : 881.57 = 386.78 : x
  2. Step 2: Convert to fraction form
    638.78/881.57 = 386.78/x
  3. Step 3: Cross multiply
    638.78x = 881.57 × 386.78
  4. Step 4: Simplify right side
    638.78x = 340,971.71
  5. Step 5: Solve for x
    x = 340,971.71/638.78
  6. Step 6: Final answer
    x = 533.79

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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.