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Finding the Fourth Proportional to 1,221, 1,684 and 778.76

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Solution

The fourth proportional to 1,221, 1,684 and 778.76 is: 1,074.06

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,221 : 1,684 = 778.76 : x
  2. Step 2: Convert to fraction form
    1,221/1,684 = 778.76/x
  3. Step 3: Cross multiply
    1,221x = 1,684 × 778.76
  4. Step 4: Simplify right side
    1,221x = 1,311,431.84
  5. Step 5: Solve for x
    x = 1,311,431.84/1,221
  6. Step 6: Final answer
    x = 1,074.06

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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.