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Finding the Fourth Proportional to 91,378.72, 136,689 and 85,780

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Solution

The fourth proportional to 91,378.72, 136,689 and 85,780 is: 128,314.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    91,378.72 : 136,689 = 85,780 : x
  2. Step 2: Convert to fraction form
    91,378.72/136,689 = 85,780/x
  3. Step 3: Cross multiply
    91,378.72x = 136,689 × 85,780
  4. Step 4: Simplify right side
    91,378.72x = 11,725,182,420
  5. Step 5: Solve for x
    x = 11,725,182,420/91,378.72
  6. Step 6: Final answer
    x = 128,314.15

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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.