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Finding the Fourth Proportional to 1,278.80, 1,918.04 and 815.20

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Solution

The fourth proportional to 1,278.80, 1,918.04 and 815.20 is: 1,222.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,278.80 : 1,918.04 = 815.20 : x
  2. Step 2: Convert to fraction form
    1,278.80/1,918.04 = 815.20/x
  3. Step 3: Cross multiply
    1,278.80x = 1,918.04 × 815.20
  4. Step 4: Simplify right side
    1,278.80x = 1,563,586.21
  5. Step 5: Solve for x
    x = 1,563,586.21/1,278.80
  6. Step 6: Final answer
    x = 1,222.70

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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.