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Finding the Fourth Proportional to 685.21, 945.45 and 390.40

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Solution

The fourth proportional to 685.21, 945.45 and 390.40 is: 538.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.21 : 945.45 = 390.40 : x
  2. Step 2: Convert to fraction form
    685.21/945.45 = 390.40/x
  3. Step 3: Cross multiply
    685.21x = 945.45 × 390.40
  4. Step 4: Simplify right side
    685.21x = 369,103.68
  5. Step 5: Solve for x
    x = 369,103.68/685.21
  6. Step 6: Final answer
    x = 538.67

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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.