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Finding the Fourth Proportional to 1,390.80, 1,918.71 and 919.20

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Solution

The fourth proportional to 1,390.80, 1,918.71 and 919.20 is: 1,268.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,390.80 : 1,918.71 = 919.20 : x
  2. Step 2: Convert to fraction form
    1,390.80/1,918.71 = 919.20/x
  3. Step 3: Cross multiply
    1,390.80x = 1,918.71 × 919.20
  4. Step 4: Simplify right side
    1,390.80x = 1,763,678.23
  5. Step 5: Solve for x
    x = 1,763,678.23/1,390.80
  6. Step 6: Final answer
    x = 1,268.10

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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.