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Finding the Fourth Proportional to 212.58, 318.80 and 90.72

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Solution

The fourth proportional to 212.58, 318.80 and 90.72 is: 136.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    212.58 : 318.80 = 90.72 : x
  2. Step 2: Convert to fraction form
    212.58/318.80 = 90.72/x
  3. Step 3: Cross multiply
    212.58x = 318.80 × 90.72
  4. Step 4: Simplify right side
    212.58x = 28,921.76
  5. Step 5: Solve for x
    x = 28,921.76/212.58
  6. Step 6: Final answer
    x = 136.05

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.