The inflation rate over the year from January 2019 to January 2020 was 2% - HSC - SSCE Mathematics Standard - Question 21 - 2020 - Paper 1

To determine the cost of the jumper in January 2019, we can use the formula for adjusting for inflation:

ext{Cost in 2019} = rac{ ext{Cost in 2020}}{1 + ext{Inflation Rate}}

Substituting the values we have:

ext{Cost in 2019} = rac{122}{1 + 0.02} = rac{122}{1.02}

Calculating this gives:

$$ext{Cost in 2019} ext{ is approximately } 119.61$$

Therefore, the cost of the jumper in January 2019 was approximately $119.61.