A robotics company sells robot vacuum cleaners. Since the newest model was introduced a while back, the old model has seen its sales fall by a consistent 30% per month. If 8,400 old
vacuum cleaners were sold this month, how many will be sold 3 months from now?

Answer : 2,881.2 vacuum cleaners will be sold three months from now.

Steps:
8400*0.7=5880 -> 1 month from now (It’s 0.7 because it decreases by 30% so 70% will remain)
5880*0.7= 4116 -> 2 months from now
4116*0.7= 2881.2 -> 3 months from now

*note that this solution is based on the assumption that the 30% refers to it decreases by 30% of the previous months amount of vacuum cleaners sold, and not the amount of vacuum cleaners sold this month. If it were based on the amount of vacuum cleaners sold this month, the answer would be 840. (8400*0.1)