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Finding the Fourth Proportional to 986.40, 1,479.60 and 858.40

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Solution

The fourth proportional to 986.40, 1,479.60 and 858.40 is: 1,287.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    986.40 : 1,479.60 = 858.40 : x
  2. Step 2: Convert to fraction form
    986.40/1,479.60 = 858.40/x
  3. Step 3: Cross multiply
    986.40x = 1,479.60 × 858.40
  4. Step 4: Simplify right side
    986.40x = 1,270,088.64
  5. Step 5: Solve for x
    x = 1,270,088.64/986.40
  6. Step 6: Final answer
    x = 1,287.60

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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.