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Finding the Fourth Proportional to 71.80, 98.85 and 64.78

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Solution

The fourth proportional to 71.80, 98.85 and 64.78 is: 89.19

Step by Step Solution

  1. Step 1: Write the proportion equation
    71.80 : 98.85 = 64.78 : x
  2. Step 2: Convert to fraction form
    71.80/98.85 = 64.78/x
  3. Step 3: Cross multiply
    71.80x = 98.85 × 64.78
  4. Step 4: Simplify right side
    71.80x = 6,403.50
  5. Step 5: Solve for x
    x = 6,403.50/71.80
  6. Step 6: Final answer
    x = 89.19

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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.