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Finding the Fourth Proportional to 156.42, 215.37 and 128.70

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Solution

The fourth proportional to 156.42, 215.37 and 128.70 is: 177.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    156.42 : 215.37 = 128.70 : x
  2. Step 2: Convert to fraction form
    156.42/215.37 = 128.70/x
  3. Step 3: Cross multiply
    156.42x = 215.37 × 128.70
  4. Step 4: Simplify right side
    156.42x = 27,718.12
  5. Step 5: Solve for x
    x = 27,718.12/156.42
  6. Step 6: Final answer
    x = 177.20

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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.