This appears to be a collection of math problems, likely from a test or homework assignment. The specific questions are embedded within the solution, such as: "Find the product of 35 and 12.", "How ma

$$35 \times 12 = 420$$

The product of 35 and 12 is $\boxed{\text{420}}$.

6. How many 180g could be obtained from 1kg?

$$\frac{1000 \text{ g}}{180 \text{ g}} \approx 5.55$$

You can obtain $\boxed{\text{5}}$ full 180g portions from 1kg.

7. A square is $36 \text{cm}^2$ in area. What is its perimeter?

The area of a square is $s^2$, where $s$ is the side length.

$$s^2 = 36 \text{ cm}^2$$ $$s = \sqrt{36 \text{ cm}^2} = 6 \text{ cm}$$

The perimeter of a square is $4s$.

$$\text{Perimeter} = 4 \times 6 \text{ cm} = 24 \text{ cm}$$

The perimeter of the square is $\boxed{\text{24 cm}}$.

8. How many centimetres are in 2.5 metres?

$$2.5 \text{ m} \times 100 \frac{\text{cm}}{\text{m}} = 250 \text{ cm}$$

There are $\boxed{\text{250 cm}}$ in 2.5 metres.

9. What fraction of a metre is 50cm?

$$\frac{50 \text{ cm}}{100 \text{ cm}} = \frac{1}{2}$$

50cm is $\boxed{\text{}\frac{1}{2}\text{}}$ of a metre.

10. Find the cost of 5 shirts with a price tag £17?

$$£17 \times 5 = £85$$

The cost of 5 shirts is $\boxed{\text{£85}}$.