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Finding the Fourth Proportional to 1,388.21, 1,915.28 and 989.93

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Solution

The fourth proportional to 1,388.21, 1,915.28 and 989.93 is: 1,365.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,388.21 : 1,915.28 = 989.93 : x
  2. Step 2: Convert to fraction form
    1,388.21/1,915.28 = 989.93/x
  3. Step 3: Cross multiply
    1,388.21x = 1,915.28 × 989.93
  4. Step 4: Simplify right side
    1,388.21x = 1,895,985.91
  5. Step 5: Solve for x
    x = 1,895,985.91/1,388.21
  6. Step 6: Final answer
    x = 1,365.78

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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.