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Finding the Fourth Proportional to 78.98, 108.80 and 64.40

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Solution

The fourth proportional to 78.98, 108.80 and 64.40 is: 88.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.98 : 108.80 = 64.40 : x
  2. Step 2: Convert to fraction form
    78.98/108.80 = 64.40/x
  3. Step 3: Cross multiply
    78.98x = 108.80 × 64.40
  4. Step 4: Simplify right side
    78.98x = 7,006.72
  5. Step 5: Solve for x
    x = 7,006.72/78.98
  6. Step 6: Final answer
    x = 88.72

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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.