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Finding the Fourth Proportional to 15.90, 21.90 and 15.40

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Solution

The fourth proportional to 15.90, 21.90 and 15.40 is: 21.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.90 : 21.90 = 15.40 : x
  2. Step 2: Convert to fraction form
    15.90/21.90 = 15.40/x
  3. Step 3: Cross multiply
    15.90x = 21.90 × 15.40
  4. Step 4: Simplify right side
    15.90x = 337.26
  5. Step 5: Solve for x
    x = 337.26/15.90
  6. Step 6: Final answer
    x = 21.21

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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.