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Finding the Fourth Proportional to 1.28, 1.91 and 0.78

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Solution

The fourth proportional to 1.28, 1.91 and 0.78 is: 1.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    1.28 : 1.91 = 0.78 : x
  2. Step 2: Convert to fraction form
    1.28/1.91 = 0.78/x
  3. Step 3: Cross multiply
    1.28x = 1.91 × 0.78
  4. Step 4: Simplify right side
    1.28x = 1.48
  5. Step 5: Solve for x
    x = 1.48/1.28
  6. Step 6: Final answer
    x = 1.16

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.