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Finding the Fourth Proportional to 1,279.76, 1,921.28 and 870.72

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Solution

The fourth proportional to 1,279.76, 1,921.28 and 870.72 is: 1,307.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,279.76 : 1,921.28 = 870.72 : x
  2. Step 2: Convert to fraction form
    1,279.76/1,921.28 = 870.72/x
  3. Step 3: Cross multiply
    1,279.76x = 1,921.28 × 870.72
  4. Step 4: Simplify right side
    1,279.76x = 1,672,896.92
  5. Step 5: Solve for x
    x = 1,672,896.92/1,279.76
  6. Step 6: Final answer
    x = 1,307.20

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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.