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Finding the Fourth Proportional to 1,138.99, 1,571.70 and 840.40

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Solution

The fourth proportional to 1,138.99, 1,571.70 and 840.40 is: 1,159.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,138.99 : 1,571.70 = 840.40 : x
  2. Step 2: Convert to fraction form
    1,138.99/1,571.70 = 840.40/x
  3. Step 3: Cross multiply
    1,138.99x = 1,571.70 × 840.40
  4. Step 4: Simplify right side
    1,138.99x = 1,320,852.75
  5. Step 5: Solve for x
    x = 1,320,852.75/1,138.99
  6. Step 6: Final answer
    x = 1,159.67

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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.