using the formula the index value will now be 1,358/1,295 x 100 = 104.9. this clearly shows that since the base period of the first week there has been an increase in quantity of 4.9%.
in week 3 the quantity was higher again so the index will have climbed even higher. the index would now be 1,412/1,295 x 100 = 109.0 showing that there has been a 9% increase since the base period of the first week.
if i knew that in week 4 the quantity index for my jam doughnut habit was going to climb further to 112.4, i could work out that this meant that i was going to eat 