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Finding the Fourth Proportional to 1,278, 1,920.78 and 869.76

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Solution

The fourth proportional to 1,278, 1,920.78 and 869.76 is: 1,307.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,278 : 1,920.78 = 869.76 : x
  2. Step 2: Convert to fraction form
    1,278/1,920.78 = 869.76/x
  3. Step 3: Cross multiply
    1,278x = 1,920.78 × 869.76
  4. Step 4: Simplify right side
    1,278x = 1,670,617.61
  5. Step 5: Solve for x
    x = 1,670,617.61/1,278
  6. Step 6: Final answer
    x = 1,307.21

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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.