Point C is taken inside the segment AB, so AC: BC = 2: 5. Find BC if AB = 21.

If AC refers to BC as 2 to 5 refers, then we can find BC under the condition that we also have the length of the entire segment AB.

The length of the entire segment is 21 cm.

If the segment AB was divided into two parts and at the same time they relate as 2 to 5, then we can determine into how many conditional equal parts the segment AB is divided into.

2 + 5 = 7 (hours) – the segment AB is divided into so many parts.

Let’s find the length of one such part.

21 cm: 7 = 3 cm – the length of one of the seven parts.

Let’s find the aircraft.

5 * 3 cm = 15 cm.

Answer: the length of the BC segment is 15 cm.