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Finding the Fourth Proportional to 780.89, 1,170.35 and 391

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Solution

The fourth proportional to 780.89, 1,170.35 and 391 is: 586.01

Step by Step Solution

  1. Step 1: Write the proportion equation
    780.89 : 1,170.35 = 391 : x
  2. Step 2: Convert to fraction form
    780.89/1,170.35 = 391/x
  3. Step 3: Cross multiply
    780.89x = 1,170.35 × 391
  4. Step 4: Simplify right side
    780.89x = 457,606.85
  5. Step 5: Solve for x
    x = 457,606.85/780.89
  6. Step 6: Final answer
    x = 586.01

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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.