Home / 781.40-1,171.20-287.60

Finding the Fourth Proportional to 781.40, 1,171.20 and 287.60

Calculator

Solution

The fourth proportional to 781.40, 1,171.20 and 287.60 is: 431.07

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.40 : 1,171.20 = 287.60 : x
  2. Step 2: Convert to fraction form
    781.40/1,171.20 = 287.60/x
  3. Step 3: Cross multiply
    781.40x = 1,171.20 × 287.60
  4. Step 4: Simplify right side
    781.40x = 336,837.12
  5. Step 5: Solve for x
    x = 336,837.12/781.40
  6. Step 6: Final answer
    x = 431.07

Related Problems

Find fourth proportional to 390.70, 585.60 and 143.80
Half scale
Find fourth proportional to 1,562.80, 2,342.40 and 575.20
Double scale
Find fourth proportional to 782.40, 1,172.70 and 288.60
Similar ratio
Find fourth proportional to 1,172.10, 1,756.80 and 431.40
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.