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Finding the Fourth Proportional to 390.54, 538.78 and 279.80

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Solution

The fourth proportional to 390.54, 538.78 and 279.80 is: 386.01

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.54 : 538.78 = 279.80 : x
  2. Step 2: Convert to fraction form
    390.54/538.78 = 279.80/x
  3. Step 3: Cross multiply
    390.54x = 538.78 × 279.80
  4. Step 4: Simplify right side
    390.54x = 150,750.64
  5. Step 5: Solve for x
    x = 150,750.64/390.54
  6. Step 6: Final answer
    x = 386.01

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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.