To find the least number of additional tickets that Kari needs to win to have enough tickets for a 20th prize, we need to determine how many more tickets are needed to make a total of 20 groups of 65 tickets.
Kari currently has 1,282 tickets, which is equal to 19 groups of 65 tickets.
To find the total number of tickets needed for 20 groups, we can multiply 20 by 65:
20 groups × 65 tickets/group = 1,300 tickets
Since Kari currently has 1,282 tickets, she needs an additional:
1,300 tickets - 1,282 tickets = 18 tickets
Therefore, Kari needs to win at least 18 additional tickets to have enough tickets for a 20th prize.