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Finding the Fourth Proportional to 113.79, 156.90 and 90.40

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Solution

The fourth proportional to 113.79, 156.90 and 90.40 is: 124.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    113.79 : 156.90 = 90.40 : x
  2. Step 2: Convert to fraction form
    113.79/156.90 = 90.40/x
  3. Step 3: Cross multiply
    113.79x = 156.90 × 90.40
  4. Step 4: Simplify right side
    113.79x = 14,183.76
  5. Step 5: Solve for x
    x = 14,183.76/113.79
  6. Step 6: Final answer
    x = 124.65

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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.