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Finding the Fourth Proportional to 1,212.40, 1,672.80 and 688.40

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Solution

The fourth proportional to 1,212.40, 1,672.80 and 688.40 is: 949.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,212.40 : 1,672.80 = 688.40 : x
  2. Step 2: Convert to fraction form
    1,212.40/1,672.80 = 688.40/x
  3. Step 3: Cross multiply
    1,212.40x = 1,672.80 × 688.40
  4. Step 4: Simplify right side
    1,212.40x = 1,151,555.52
  5. Step 5: Solve for x
    x = 1,151,555.52/1,212.40
  6. Step 6: Final answer
    x = 949.81

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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.