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Finding the Fourth Proportional to 1,385.40, 1,911.80 and 764.40

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Solution

The fourth proportional to 1,385.40, 1,911.80 and 764.40 is: 1,054.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,385.40 : 1,911.80 = 764.40 : x
  2. Step 2: Convert to fraction form
    1,385.40/1,911.80 = 764.40/x
  3. Step 3: Cross multiply
    1,385.40x = 1,911.80 × 764.40
  4. Step 4: Simplify right side
    1,385.40x = 1,461,379.92
  5. Step 5: Solve for x
    x = 1,461,379.92/1,385.40
  6. Step 6: Final answer
    x = 1,054.84

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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.