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Finding the Fourth Proportional to 1,311.68, 1,811.70 and 981.57

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Solution

The fourth proportional to 1,311.68, 1,811.70 and 981.57 is: 1,355.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,311.68 : 1,811.70 = 981.57 : x
  2. Step 2: Convert to fraction form
    1,311.68/1,811.70 = 981.57/x
  3. Step 3: Cross multiply
    1,311.68x = 1,811.70 × 981.57
  4. Step 4: Simplify right side
    1,311.68x = 1,778,310.37
  5. Step 5: Solve for x
    x = 1,778,310.37/1,311.68
  6. Step 6: Final answer
    x = 1,355.76

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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.