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Finding the Fourth Proportional to 780.78, 1,170.90 and 260.70

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Solution

The fourth proportional to 780.78, 1,170.90 and 260.70 is: 390.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    780.78 : 1,170.90 = 260.70 : x
  2. Step 2: Convert to fraction form
    780.78/1,170.90 = 260.70/x
  3. Step 3: Cross multiply
    780.78x = 1,170.90 × 260.70
  4. Step 4: Simplify right side
    780.78x = 305,253.63
  5. Step 5: Solve for x
    x = 305,253.63/780.78
  6. Step 6: Final answer
    x = 390.96

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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.