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Finding the Fourth Proportional to 1,056.40, 1,581.90 and 840.40

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Solution

The fourth proportional to 1,056.40, 1,581.90 and 840.40 is: 1,258.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,056.40 : 1,581.90 = 840.40 : x
  2. Step 2: Convert to fraction form
    1,056.40/1,581.90 = 840.40/x
  3. Step 3: Cross multiply
    1,056.40x = 1,581.90 × 840.40
  4. Step 4: Simplify right side
    1,056.40x = 1,329,428.76
  5. Step 5: Solve for x
    x = 1,329,428.76/1,056.40
  6. Step 6: Final answer
    x = 1,258.45

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.