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Finding the Fourth Proportional to 89.76, 123.78 and 57

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Solution

The fourth proportional to 89.76, 123.78 and 57 is: 78.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    89.76 : 123.78 = 57 : x
  2. Step 2: Convert to fraction form
    89.76/123.78 = 57/x
  3. Step 3: Cross multiply
    89.76x = 123.78 × 57
  4. Step 4: Simplify right side
    89.76x = 7,055.46
  5. Step 5: Solve for x
    x = 7,055.46/89.76
  6. Step 6: Final answer
    x = 78.60

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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.