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Finding the Fourth Proportional to 78, 116.40 and 74.88

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Solution

The fourth proportional to 78, 116.40 and 74.88 is: 111.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    78 : 116.40 = 74.88 : x
  2. Step 2: Convert to fraction form
    78/116.40 = 74.88/x
  3. Step 3: Cross multiply
    78x = 116.40 × 74.88
  4. Step 4: Simplify right side
    78x = 8,716.03
  5. Step 5: Solve for x
    x = 8,716.03/78
  6. Step 6: Final answer
    x = 111.74

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.