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Finding the Fourth Proportional to 1,390.20, 1,918.80 and 918.18

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Solution

The fourth proportional to 1,390.20, 1,918.80 and 918.18 is: 1,267.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.20 : 1,918.80 = 918.18 : x
  2. Step 2: Convert to fraction form
    1,390.20/1,918.80 = 918.18/x
  3. Step 3: Cross multiply
    1,390.20x = 1,918.80 × 918.18
  4. Step 4: Simplify right side
    1,390.20x = 1,761,803.78
  5. Step 5: Solve for x
    x = 1,761,803.78/1,390.20
  6. Step 6: Final answer
    x = 1,267.30

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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.