Question

Every week I buy four 2-litre bottles of lemonade whilst shopping at my local supermarket. Last week the bottles on the shelf were limited edition “2.5 litres for the price of 2 litres” bottles, and the supermarket also had a “buy 3 bottles, get another one free” offer.

In terms of cost per litre, by what percentage was the cost of my four bottles of lemonade lower than usual last week?

Answer 1

40%

Explanation:

Every week you he buys 4 number of 2 Litres bottle of lemonade.

Thus, let's say cost of each bottle is X.

This means he total cost is 4X

Now, total litres = 4 × 2 = 8 litres

Thus, cost per litre = 4X/8 = ½X

Now, we are told that Last week the bottles on the shelf were limited edition “2.5 litres for the price of 2 litres” bottles ".

This means that now, it is cheaper.

However, the supermarket also had a “buy 3 bottles, get another one free” offer.

Now since he buys 8 litres weekly, now since it's 2.5 L bottle, he will buy 3 since he will be given 1 free for every 3 he buys.

Thus, total litres he is paying for = 2.5 × 3 = 7.5 litres

Thus, cost per bottle is; 3X

Since he is getting 1 bottle free, then total bottle he gets is; 7.5 L + 2.5 L = 10L

Thus;

cost per litre is now; 3X/10

Difference in costs per litre is;

½X - 3X/10 = X/5

percentage of the cost of four bottles of lemonade lower than usual last week = (X/5)/(½X) × 100% = 2/5 × 100% = 40%