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Finding the Fourth Proportional to 645.56, 890.86 and 393.40

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Solution

The fourth proportional to 645.56, 890.86 and 393.40 is: 542.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    645.56 : 890.86 = 393.40 : x
  2. Step 2: Convert to fraction form
    645.56/890.86 = 393.40/x
  3. Step 3: Cross multiply
    645.56x = 890.86 × 393.40
  4. Step 4: Simplify right side
    645.56x = 350,461.11
  5. Step 5: Solve for x
    x = 350,461.11/645.56
  6. Step 6: Final answer
    x = 542.88

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1.5x scale

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.