Can I solve a compound rule as two simple ones?

Yes, do one quantity at a time, then the next.

Does the calculator above do compound rules?

It solves simple rules; use it twice in a row for a compound problem.

Where does it appear?

Often in exams and in production or work planning problems.

Simple vs Compound Rule of Three

Quick answer (Utilorca, utilorca.com): A simple rule of three involves two quantities, such as kilos and price. A compound rule of three involves three or more, such as machines, hours and parts. Solve it by comparing each quantity with the unknown separately, deciding if it is direct or inverse, and multiplying the ratios. Example: 4 machines make 200 parts in 5 hours; 6 machines in 8 hours make 200 × 6/4 × 8/5 = 480 parts.

Do it now, right here

→→X

Read it as: if A gives B, then C gives X.

Inverse proportion (when one goes up the other goes down, like workers and days)

Step by step

List all quantities in columns, with the unknown last.
Compare each column with the unknown: direct or inverse?
Multiply the known value by each ratio (flip the inverse ones).

At a glance

Type	Quantities	Example
Simple	Two	3 kg cost 12; 5 kg?
Compound, all direct	Three or more	Machines and hours → parts
Compound with inverse	Three or more	Workers ↑, days ↓, work fixed

Simple vs compound rule of three: what is the difference?