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Finding the Fourth Proportional to 978.40, 1,464.40 and 690.40

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Solution

The fourth proportional to 978.40, 1,464.40 and 690.40 is: 1,033.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    978.40 : 1,464.40 = 690.40 : x
  2. Step 2: Convert to fraction form
    978.40/1,464.40 = 690.40/x
  3. Step 3: Cross multiply
    978.40x = 1,464.40 × 690.40
  4. Step 4: Simplify right side
    978.40x = 1,011,021.76
  5. Step 5: Solve for x
    x = 1,011,021.76/978.40
  6. Step 6: Final answer
    x = 1,033.34

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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.