Final answer:
Sian's lemon drink is 40% concentrate, calculated by dividing the volume of the concentrate by the total volume of the drink and multiplying by 100.
Step-by-step explanation:
To calculate the percentage of concentrate in Sian's lemon drink, we combine the volume of concentrate with the volume of water to find the total volume of the drink, and then figure out the concentration ratio. Sian mixed 120ml of concentrate with 180ml of water, so the total volume of the drink is 120ml + 180ml = 300ml. To find out what percentage of the drink is concentrate, we use the formula:
Percentage of concentrate = (Volume of concentrate ÷ Total volume of drink) x 100%
Substituting the values, we get:
Percentage of concentrate = (120ml ÷ 300ml) x 100% = 40%
Therefore, 40% of Sian's lemon drink is concentrate.