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Finding the Fourth Proportional to 1,290.60, 1,780.65 and 812.10

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Solution

The fourth proportional to 1,290.60, 1,780.65 and 812.10 is: 1,120.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,290.60 : 1,780.65 = 812.10 : x
  2. Step 2: Convert to fraction form
    1,290.60/1,780.65 = 812.10/x
  3. Step 3: Cross multiply
    1,290.60x = 1,780.65 × 812.10
  4. Step 4: Simplify right side
    1,290.60x = 1,446,065.87
  5. Step 5: Solve for x
    x = 1,446,065.87/1,290.60
  6. Step 6: Final answer
    x = 1,120.46

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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.