Answer:
4 and 13
Step-by-step explanation:
You want integer solutions to ...
15 ≤ n(n+1) ≤ 200
If we let the limits be represented by "a", then the equality is represented by ...
n² +n -a = 0
(n² +n +1/4) -a -1/4 = 0
(n +1/2)^2 = (a +1/4)
n = -1/2 + √(a +1/4)
For a=15, we have
n ≥ -1/2 + √15.25 ≈ 3.4 . . . . . minimum n is 4
For a=200, we have
n ≤ -1/2 + √200.25 ≈ 13.7 . . . maximum n is 13
The least and greatest integers on the cards are 4 and 13.
