A bit of mathematical sleight-of-hand going on there, cee-dee...

Both you and the Daily Mail are correct. Let me explain:

1. The rule of maths is BODMAS - Brackets of Division, Multiplication, Addition, Subtraction - and therefore in the example given by the Daily Mail the correct answer is 590, as the 450 is Divided by 5 before being (correctly) Added to 500.

2. In your example you ignore the use of invisible Brackets: if a baker bakes a batch of 500 loaves and then bakes a second batch of 450 loaves he has (500 + 450) = 950 loaves. He then divides the total number of loves between 5 different supermarkets, sending 950 Divided by 5 (190) loaves to each.

My maths teacher once "proved" that 2 equals 1 using a not dissimilar mathematical sleight-of-hand.