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Finding the Fourth Proportional to 7.81, 10.78 and 7.00

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Solution

The fourth proportional to 7.81, 10.78 and 7.00 is: 9.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    7.81 : 10.78 = 7.00 : x
  2. Step 2: Convert to fraction form
    7.81/10.78 = 7.00/x
  3. Step 3: Cross multiply
    7.81x = 10.78 × 7.00
  4. Step 4: Simplify right side
    7.81x = 75.42
  5. Step 5: Solve for x
    x = 75.42/7.81
  6. Step 6: Final answer
    x = 9.66

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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.