Home / 815.78-1,221.78-405.20

Finding the Fourth Proportional to 815.78, 1,221.78 and 405.20

Calculator

Solution

The fourth proportional to 815.78, 1,221.78 and 405.20 is: 606.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    815.78 : 1,221.78 = 405.20 : x
  2. Step 2: Convert to fraction form
    815.78/1,221.78 = 405.20/x
  3. Step 3: Cross multiply
    815.78x = 1,221.78 × 405.20
  4. Step 4: Simplify right side
    815.78x = 495,065.26
  5. Step 5: Solve for x
    x = 495,065.26/815.78
  6. Step 6: Final answer
    x = 606.86

Related Problems

Find fourth proportional to 407.89, 610.89 and 202.60
Half scale
Find fourth proportional to 1,631.56, 2,443.56 and 810.40
Double scale
Find fourth proportional to 816.78, 1,223.28 and 406.20
Similar ratio
Find fourth proportional to 1,223.67, 1,832.67 and 607.80
1.5x scale

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.