You have 60 tyres to build tyre swings, balancing beams, and climbing walls in the ratio 3:2:1. How many tyres will be used for the tyre swings?

The ratio for tyre swings, balancing beams, and climbing walls is 3:2:1.

$$\text{Total parts} = 3 + 2 + 1 = 6$$

There are 60 tyres in total.

$$\text{Value of one part} = \frac{60 \text{ tyres}}{6 \text{ parts}}$$ $$\text{Value of one part} = 10 \text{ tyres/part}$$

Tyre swings correspond to 3 parts of the ratio.

$$\text{Tyres for swings} = 3 \times 10 \text{ tyres/part}$$ $$\text{Tyres for swings} = 30 \text{ tyres}$$

The number of tyres used for the tyre swings is $\text{30 tyres}$.