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Finding the Fourth Proportional to 1,121.65, 1,680.45 and 688.30

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Solution

The fourth proportional to 1,121.65, 1,680.45 and 688.30 is: 1,031.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.65 : 1,680.45 = 688.30 : x
  2. Step 2: Convert to fraction form
    1,121.65/1,680.45 = 688.30/x
  3. Step 3: Cross multiply
    1,121.65x = 1,680.45 × 688.30
  4. Step 4: Simplify right side
    1,121.65x = 1,156,653.74
  5. Step 5: Solve for x
    x = 1,156,653.74/1,121.65
  6. Step 6: Final answer
    x = 1,031.21

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.