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Finding the Fourth Proportional to 15.78, 21.74 and 15.57

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Solution

The fourth proportional to 15.78, 21.74 and 15.57 is: 21.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.78 : 21.74 = 15.57 : x
  2. Step 2: Convert to fraction form
    15.78/21.74 = 15.57/x
  3. Step 3: Cross multiply
    15.78x = 21.74 × 15.57
  4. Step 4: Simplify right side
    15.78x = 338.49
  5. Step 5: Solve for x
    x = 338.49/15.78
  6. Step 6: Final answer
    x = 21.45

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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.