Its simple!. All you have to do is: Convert each price to a price per kilogram. [Or price per litre if the item is a liquid.] Then choose the cheapest price. Note! There are several different ways to do the maths. This PowerPoint shows only one of the ways.
$20.78 for 1 kg is less than $22.59 for 1 kg.
The red 180g packet is better value for money.
The smaller packet is the better value.
1L = 1000 ml
One small packet weighs 45g.
1000 ÷ 45 =
packets weigh 1 kg
One small packet costs $1.99.
× $1.99 = $44.22
45g for $1.99 is equivalent to $44.22 per kilogram.
One 500g packet of Sultana Bran costs $5.79.
Two packets of 500g Sultana Bran make 1 kg.
2 × $5.79 = $11.58
500g for $5.79 is equivalent to $11.58 per kilogram.
The large 820g box of Sultana Bran costs $7.41.
1000 ÷ 820 =
boxes of 820g sultana Bran make 1 kg.
× $7.41 = $9.04