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Finding the Fourth Proportional to 1,421.84, 1,961.80 and 979.60

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Solution

The fourth proportional to 1,421.84, 1,961.80 and 979.60 is: 1,351.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,421.84 : 1,961.80 = 979.60 : x
  2. Step 2: Convert to fraction form
    1,421.84/1,961.80 = 979.60/x
  3. Step 3: Cross multiply
    1,421.84x = 1,961.80 × 979.60
  4. Step 4: Simplify right side
    1,421.84x = 1,921,779.28
  5. Step 5: Solve for x
    x = 1,921,779.28/1,421.84
  6. Step 6: Final answer
    x = 1,351.61

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.