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Finding the Fourth Proportional to 72.78, 100.40 and 56.40

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Solution

The fourth proportional to 72.78, 100.40 and 56.40 is: 77.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    72.78 : 100.40 = 56.40 : x
  2. Step 2: Convert to fraction form
    72.78/100.40 = 56.40/x
  3. Step 3: Cross multiply
    72.78x = 100.40 × 56.40
  4. Step 4: Simplify right side
    72.78x = 5,662.28
  5. Step 5: Solve for x
    x = 5,662.28/72.78
  6. Step 6: Final answer
    x = 77.80

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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.