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Finding the Fourth Proportional to 999.40, 1,378.74 and 688.36

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Solution

The fourth proportional to 999.40, 1,378.74 and 688.36 is: 949.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    999.40 : 1,378.74 = 688.36 : x
  2. Step 2: Convert to fraction form
    999.40/1,378.74 = 688.36/x
  3. Step 3: Cross multiply
    999.40x = 1,378.74 × 688.36
  4. Step 4: Simplify right side
    999.40x = 949,069.47
  5. Step 5: Solve for x
    x = 949,069.47/999.40
  6. Step 6: Final answer
    x = 949.64

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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.