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Finding the Fourth Proportional to 390.21, 538.50 and 215.55

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Solution

The fourth proportional to 390.21, 538.50 and 215.55 is: 297.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.21 : 538.50 = 215.55 : x
  2. Step 2: Convert to fraction form
    390.21/538.50 = 215.55/x
  3. Step 3: Cross multiply
    390.21x = 538.50 × 215.55
  4. Step 4: Simplify right side
    390.21x = 116,075.19
  5. Step 5: Solve for x
    x = 116,075.19/390.21
  6. Step 6: Final answer
    x = 297.47

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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.