Home / 870.90-1,305.81-408.78

Finding the Fourth Proportional to 870.90, 1,305.81 and 408.78

Calculator

Solution

The fourth proportional to 870.90, 1,305.81 and 408.78 is: 612.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    870.90 : 1,305.81 = 408.78 : x
  2. Step 2: Convert to fraction form
    870.90/1,305.81 = 408.78/x
  3. Step 3: Cross multiply
    870.90x = 1,305.81 × 408.78
  4. Step 4: Simplify right side
    870.90x = 533,789.01
  5. Step 5: Solve for x
    x = 533,789.01/870.90
  6. Step 6: Final answer
    x = 612.92

Related Problems

Find fourth proportional to 435.45, 652.91 and 204.39
Half scale
Find fourth proportional to 1,741.80, 2,611.62 and 817.56
Double scale
Find fourth proportional to 871.90, 1,307.31 and 409.78
Similar ratio
Find fourth proportional to 1,306.35, 1,958.72 and 613.17
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.