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Finding the Fourth Proportional to 78.96, 109.20 and 71.70

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Solution

The fourth proportional to 78.96, 109.20 and 71.70 is: 99.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.96 : 109.20 = 71.70 : x
  2. Step 2: Convert to fraction form
    78.96/109.20 = 71.70/x
  3. Step 3: Cross multiply
    78.96x = 109.20 × 71.70
  4. Step 4: Simplify right side
    78.96x = 7,829.64
  5. Step 5: Solve for x
    x = 7,829.64/78.96
  6. Step 6: Final answer
    x = 99.16

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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.