Problems 7, 8, and 9 involving cost price, selling price, and profit calculations.

Here are the solutions to problems 7, 8, and 9.

7.

Step 1: Calculate the cost price per kg of meat.
Total cost = Gh¢22.40
Total quantity = 250 kg

$$\text{Cost Price per kg (CP/kg)} = \frac{\text{Total Cost}}{\text{Total Quantity}}$$ $$\text{CP/kg} = \frac{\text{Gh¢}22.40}{250 \text{ kg}}$$ $$\text{CP/kg} = \text{Gh¢}0.0896 \text{ per kg}$$

Step 2: Calculate the selling price per kg to make a 25% profit.
Profit percentage = 25% = 0.25

$$\text{Selling Price per kg (SP/kg)} = \text{CP/kg} \times (1 + \text{Profit Percentage})$$ $$\text{SP/kg} = \text{Gh¢}0.0896 \times (1 + 0.25)$$ $$\text{SP/kg} = \text{Gh¢}0.0896 \times 1.25$$ $$\text{SP/kg} = \text{Gh¢}0.112$$

He should retail it at $\boxed{\text{Gh¢}0.112 \text{ per kg}}$.

8.

Step 1: Calculate the cost price per kg of tomatoes.
Total cost = Gh¢5.20
Total quantity = 130 kg

$$\text{Cost Price per kg (CP/kg)} = \frac{\text{Gh¢}5.20}{130 \text{ kg}}$$ $$\text{CP/kg} = \text{Gh¢}0.04 \text{ per kg}$$

Step 2: Calculate the selling price and revenue for the first half of the tomatoes.
Quantity for first half = $\frac{130 \text{ kg}}{2} = 65 \text{ kg}$
Profit percentage for first half = 30% = 0.30

$$\text{SP}_1 \text{ per kg} = \text{CP/kg} \times (1 + 0.30)$$ $$\text{SP}_1 \text{ per kg} = \text{Gh¢}0.04 \times 1.30$$ $$\text{SP}_1 \text{ per kg} = \text{Gh¢}0.052 \text{ per kg}$$

Revenue from first half = $65 \text{ kg} \times \text{Gh¢}0.052 \text{ per kg} = \text{Gh¢}3.38$

Step 3: Calculate the quantity for the second half and the amount thrown away.
Quantity remaining after first half = $130 \text{ kg} - 65 \text{ kg} = 65 \text{ kg}$
Quantity thrown away = 5 kg
Quantity sold in second half = $65 \text{ kg} - 5 \text{ kg} = 60 \text{ kg}$