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Finding the Fourth Proportional to 1,278.50, 1,917.76 and 509

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Solution

The fourth proportional to 1,278.50, 1,917.76 and 509 is: 763.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,278.50 : 1,917.76 = 509 : x
  2. Step 2: Convert to fraction form
    1,278.50/1,917.76 = 509/x
  3. Step 3: Cross multiply
    1,278.50x = 1,917.76 × 509
  4. Step 4: Simplify right side
    1,278.50x = 976,139.84
  5. Step 5: Solve for x
    x = 976,139.84/1,278.50
  6. Step 6: Final answer
    x = 763.50

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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.