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Finding the Fourth Proportional to 72, 99.78 and 70.80

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Solution

The fourth proportional to 72, 99.78 and 70.80 is: 98.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    72 : 99.78 = 70.80 : x
  2. Step 2: Convert to fraction form
    72/99.78 = 70.80/x
  3. Step 3: Cross multiply
    72x = 99.78 × 70.80
  4. Step 4: Simplify right side
    72x = 7,064.42
  5. Step 5: Solve for x
    x = 7,064.42/72
  6. Step 6: Final answer
    x = 98.12

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Why These Related Problems?

These problems maintain the same ratio (1.39) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.