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Finding the Fourth Proportional to 1,221.65, 1,685.91 and 690.63

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Solution

The fourth proportional to 1,221.65, 1,685.91 and 690.63 is: 953.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,221.65 : 1,685.91 = 690.63 : x
  2. Step 2: Convert to fraction form
    1,221.65/1,685.91 = 690.63/x
  3. Step 3: Cross multiply
    1,221.65x = 1,685.91 × 690.63
  4. Step 4: Simplify right side
    1,221.65x = 1,164,336.29
  5. Step 5: Solve for x
    x = 1,164,336.29/1,221.65
  6. Step 6: Final answer
    x = 953.09

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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.