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Finding the Fourth Proportional to 1,221.23, 1,685 and 690.12

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Solution

The fourth proportional to 1,221.23, 1,685 and 690.12 is: 952.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,221.23 : 1,685 = 690.12 : x
  2. Step 2: Convert to fraction form
    1,221.23/1,685 = 690.12/x
  3. Step 3: Cross multiply
    1,221.23x = 1,685 × 690.12
  4. Step 4: Simplify right side
    1,221.23x = 1,162,852.20
  5. Step 5: Solve for x
    x = 1,162,852.20/1,221.23
  6. Step 6: Final answer
    x = 952.20

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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.