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Finding the Fourth Proportional to 931.20, 1,389.60 and 821.76

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Solution

The fourth proportional to 931.20, 1,389.60 and 821.76 is: 1,226.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    931.20 : 1,389.60 = 821.76 : x
  2. Step 2: Convert to fraction form
    931.20/1,389.60 = 821.76/x
  3. Step 3: Cross multiply
    931.20x = 1,389.60 × 821.76
  4. Step 4: Simplify right side
    931.20x = 1,141,917.70
  5. Step 5: Solve for x
    x = 1,141,917.70/931.20
  6. Step 6: Final answer
    x = 1,226.29

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.