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Finding the Fourth Proportional to 211.85, 317.88 and 90.21

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Solution

The fourth proportional to 211.85, 317.88 and 90.21 is: 135.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    211.85 : 317.88 = 90.21 : x
  2. Step 2: Convert to fraction form
    211.85/317.88 = 90.21/x
  3. Step 3: Cross multiply
    211.85x = 317.88 × 90.21
  4. Step 4: Simplify right side
    211.85x = 28,675.95
  5. Step 5: Solve for x
    x = 28,675.95/211.85
  6. Step 6: Final answer
    x = 135.36

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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.