Apply general term formula of an AP, to find the total numbers of cards.
Here a (first term) = 6, d (common difference) = 1 and l( last term) = 70
l = a + (n-1)d
70 = 6 + (n-1)(1)
n = 65
Total number of cards = 65
(i) Favorable outcome = a one-digit number = 6, 7, 8, 9
Favorable number of outcomes = 4
P(getting a one-digit number) = 4/65
(ii) Favorable outcome = a number divisible by 5 = 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70
Favorable number of outcomes = 13
P(getting a number divisible by 5) = 13/65 = 1/5
(iii) Favorable outcome = an odd number less than 30 = 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27 and 29
Favorable number of outcomes = 12
P (getting a odd number less than 30) = 12/65
(iv) Favorable outcome = a composite number between 50 and 70 = 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69
The number of favorable outcomes = 15
P(getting a composite number between 50 and 70) = 15/65 = 3/13