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Finding the Fourth Proportional to 261.80, 392.65 and 79.21

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Solution

The fourth proportional to 261.80, 392.65 and 79.21 is: 118.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    261.80 : 392.65 = 79.21 : x
  2. Step 2: Convert to fraction form
    261.80/392.65 = 79.21/x
  3. Step 3: Cross multiply
    261.80x = 392.65 × 79.21
  4. Step 4: Simplify right side
    261.80x = 31,101.81
  5. Step 5: Solve for x
    x = 31,101.81/261.80
  6. Step 6: Final answer
    x = 118.80

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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.