Home / 1,311-1,809.20-721.59

Finding the Fourth Proportional to 1,311, 1,809.20 and 721.59

Calculator

Solution

The fourth proportional to 1,311, 1,809.20 and 721.59 is: 995.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,311 : 1,809.20 = 721.59 : x
  2. Step 2: Convert to fraction form
    1,311/1,809.20 = 721.59/x
  3. Step 3: Cross multiply
    1,311x = 1,809.20 × 721.59
  4. Step 4: Simplify right side
    1,311x = 1,305,497.02
  5. Step 5: Solve for x
    x = 1,305,497.02/1,311
  6. Step 6: Final answer
    x = 995.80

Related Problems

Find fourth proportional to 655.50, 904.60 and 360.80
Half scale
Find fourth proportional to 2,622, 3,618.39 and 1,443.18
Double scale
Find fourth proportional to 1,312, 1,810.58 and 722.59
Similar ratio
Find fourth proportional to 1,966.50, 2,713.79 and 1,082.39
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.