A shop sells orange juice in the following ways: 500 ml bottle for £1.15
1.5 l carton for £2.70 each or 2 cartons for £5
3.5 l carton for £5.75

What's the cheapest way of buying exactly 9 litres with no extra?
Find the amount of each type of bottle or carton you need and the total cost of buying 9 litres.

The cheapest way to purchase 9 liters of orange juice would be to buy 3 promotions of 2 1.5 liter bottles of drink at £ 5 each promotion, totaling £ 15.

Step-by-step explanation:

To obtain the cheapest way to buy 9 liters of orange juice, the cost per liter of each type of container must be determined:

500 ml bottle = £1.15 (£2.30 per liter)

1.5 l carton = £2.70 (£1.80 per liter)

2 cartons of 1.5 l = £5 (£1.66 per liter)

3.5 l carton = £5.75 (£1.64 per liter)

Thus, there is in principle a staggered way to buy the drink: 2 cartons of 3.5 liters, plus 1 carton of 1.5 liters, plus 1 bottle of 500 ml, which would add up to a total cost of £15.35 (5.75 x 2 + 2.70 + 1.15) .

Now, you could also take advantage of the promotion of 2 cartons of 1.5 l at £5, with which buying 3 of these promotions would acquire the 9 liters of drink (1.5 x 2 x 3) at £15 (3 x 5).

Thus, the cheapest way to purchase 9 liters of orange juice would be to buy 3 promotions of 2 1.5 liter bottles of drink at £ 5 each promotion, totaling £ 15.