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Finding the Fourth Proportional to 1,215.20, 1,677.60 and 861.20

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Solution

The fourth proportional to 1,215.20, 1,677.60 and 861.20 is: 1,188.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,215.20 : 1,677.60 = 861.20 : x
  2. Step 2: Convert to fraction form
    1,215.20/1,677.60 = 861.20/x
  3. Step 3: Cross multiply
    1,215.20x = 1,677.60 × 861.20
  4. Step 4: Simplify right side
    1,215.20x = 1,444,749.12
  5. Step 5: Solve for x
    x = 1,444,749.12/1,215.20
  6. Step 6: Final answer
    x = 1,188.90

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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.