Cards marked with numbers 1, 3, 5… 49 are placed in a box and mixed thoroughly. One card is drawn from the box. Find the probability that the number on the card is
a composite number
As the numbers of cards in an AP, with first term a = 1 and common difference d = 2
Let the no of cards be 'n'
Number on nth card = 49
⇒ a + (n - 1)d = 49 [As nth term of an AP = a + (n - 1)d ]
⇒ 1 + (n - 1)2 = 49
⇒ (n - 1)2 = 48
⇒ n - 1 = 24
⇒ n = 25
Total No of cards = 25
Cards having a composite no = {9, 15, 21, 25, 27, 28, 33, 35, 39, 45, 49}
No of cards having a composite no = 11
We know that,
Probability of an event 
⇒ Probability of getting a card having a composite no
Couldn't generate an explanation.
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