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Finding the Fourth Proportional to 1,393.08, 1,921.74 and 978.36

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Solution

The fourth proportional to 1,393.08, 1,921.74 and 978.36 is: 1,349.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,393.08 : 1,921.74 = 978.36 : x
  2. Step 2: Convert to fraction form
    1,393.08/1,921.74 = 978.36/x
  3. Step 3: Cross multiply
    1,393.08x = 1,921.74 × 978.36
  4. Step 4: Simplify right side
    1,393.08x = 1,880,153.55
  5. Step 5: Solve for x
    x = 1,880,153.55/1,393.08
  6. Step 6: Final answer
    x = 1,349.64

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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.