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Finding the Fourth Proportional to 83.90, 115.88 and 56.40

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Solution

The fourth proportional to 83.90, 115.88 and 56.40 is: 77.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    83.90 : 115.88 = 56.40 : x
  2. Step 2: Convert to fraction form
    83.90/115.88 = 56.40/x
  3. Step 3: Cross multiply
    83.90x = 115.88 × 56.40
  4. Step 4: Simplify right side
    83.90x = 6,535.63
  5. Step 5: Solve for x
    x = 6,535.63/83.90
  6. Step 6: Final answer
    x = 77.90

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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.