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Finding the Fourth Proportional to 1,390.13, 2,081.04 and 840.64

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Solution

The fourth proportional to 1,390.13, 2,081.04 and 840.64 is: 1,258.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.13 : 2,081.04 = 840.64 : x
  2. Step 2: Convert to fraction form
    1,390.13/2,081.04 = 840.64/x
  3. Step 3: Cross multiply
    1,390.13x = 2,081.04 × 840.64
  4. Step 4: Simplify right side
    1,390.13x = 1,749,405.47
  5. Step 5: Solve for x
    x = 1,749,405.47/1,390.13
  6. Step 6: Final answer
    x = 1,258.45

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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.