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Finding the Fourth Proportional to 1,390.21, 1,917.75 and 859.39

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Solution

The fourth proportional to 1,390.21, 1,917.75 and 859.39 is: 1,185.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.21 : 1,917.75 = 859.39 : x
  2. Step 2: Convert to fraction form
    1,390.21/1,917.75 = 859.39/x
  3. Step 3: Cross multiply
    1,390.21x = 1,917.75 × 859.39
  4. Step 4: Simplify right side
    1,390.21x = 1,648,095.17
  5. Step 5: Solve for x
    x = 1,648,095.17/1,390.21
  6. Step 6: Final answer
    x = 1,185.50

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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.