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Finding the Fourth Proportional to 978.78, 1,349.78 and 663.96

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Solution

The fourth proportional to 978.78, 1,349.78 and 663.96 is: 915.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    978.78 : 1,349.78 = 663.96 : x
  2. Step 2: Convert to fraction form
    978.78/1,349.78 = 663.96/x
  3. Step 3: Cross multiply
    978.78x = 1,349.78 × 663.96
  4. Step 4: Simplify right side
    978.78x = 896,199.93
  5. Step 5: Solve for x
    x = 896,199.93/978.78
  6. Step 6: Final answer
    x = 915.63

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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.