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Finding the Fourth Proportional to 2,139.60, 3,208.85 and 678.77

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Solution

The fourth proportional to 2,139.60, 3,208.85 and 678.77 is: 1,017.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    2,139.60 : 3,208.85 = 678.77 : x
  2. Step 2: Convert to fraction form
    2,139.60/3,208.85 = 678.77/x
  3. Step 3: Cross multiply
    2,139.60x = 3,208.85 × 678.77
  4. Step 4: Simplify right side
    2,139.60x = 2,178,071.11
  5. Step 5: Solve for x
    x = 2,178,071.11/2,139.60
  6. Step 6: Final answer
    x = 1,017.98

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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.