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Finding the Fourth Proportional to 990.90, 1,388.70 and 990.90

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Solution

The fourth proportional to 990.90, 1,388.70 and 990.90 is: 1,388.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.90 : 1,388.70 = 990.90 : x
  2. Step 2: Convert to fraction form
    990.90/1,388.70 = 990.90/x
  3. Step 3: Cross multiply
    990.90x = 1,388.70 × 990.90
  4. Step 4: Simplify right side
    990.90x = 1,376,062.83
  5. Step 5: Solve for x
    x = 1,376,062.83/990.90
  6. Step 6: Final answer
    x = 1,388.70

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Why These Related Problems?

These problems maintain the same ratio (1.40) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.