Bag/ Box / Piggy bank
Bag/ Box / Piggy bank
Last updated at April 16, 2024 by Teachoo
Ex 14.1, 18 A box contains 90 discs which are numbered from 1 to 90. If one disc is drawn at random from the box, find the probability that it bears a two-digit number Total number of discs = 90 Number of two digit numbers in the discs = 10, 11, 12, 13, 14,โฆโฆ, 90 Counting number of two digit numbers 10, 11, 12, 13, 14,โฆโฆ, 90 Since difference between consecutive numbers is same, These numbers form an A.P. First number = a = 10 Common difference = d = 11 โ 10 = 1 Last number = an = 90 Now, an = a + (n โ 1)d 90 = 10 + (n โ 1) 1 90 = 10 + n โ 1 90 = 9 + n n = 90 โ 9 n = 81 โด Total number of two-digit numbers between 1 and 90 = 81 So, Total number of discs with two digit numbers = 81 Now, P (getting a two-digit number) = (๐๐๐ก๐๐ ๐๐ข๐๐๐๐ ๐๐ ๐๐๐ ๐๐ ๐ค๐๐กโ ๐ก๐ค๐ ๐๐๐๐๐ก ๐๐ข๐๐๐๐)/(๐๐๐ก๐๐ ๐๐ข๐๐๐๐ ๐๐ ๐๐๐ ๐๐ ) = 81/90 = ๐/๐๐ Ex 14.1, 18 A box contains 90 discs which are numbered from 1 to 90. If one disc is drawn at random from the box, find the probability that it bears (ii) a perfect square number Total number of discs = 90 Perfect square number is a number like 1 (= 12) , 4 (= 22) , 9 (= 32) , 16 (= 42), 25(= 52) , 36 (= 62) , 49 (= 72) , 64 (= 82), 81 (= 92) Total number of discs with perfect square number = 9 P (getting a perfect square number) = (๐๐๐ก๐๐ ๐๐ข๐๐๐๐ ๐๐ ๐๐๐ ๐๐ ๐ค๐๐กโ ๐๐๐๐๐๐๐ก ๐ ๐๐ข๐๐๐ ๐๐ข๐๐๐๐)/(๐๐๐ก๐๐ ๐๐ข๐๐๐๐ ๐๐ ๐๐๐ ๐๐ ) = 9/90 = ๐/๐๐ Ex 14.1, 18 A box contains 90 discs which are numbered from 1 to 90. If one disc is drawn at random from the box, find the probability that it bears (iii) Number divisible by 5 Total number of discs = 90 Numbers divisible by 5 are 5 , 10, 15, 20 , 25 , 30 , 35 ,40 , 45 , 50 , 55 , 60 , 65 , 70 , 75 , 80 , 85 , 90 Total number of numbers on the disc divisible by 5 = 18 P (getting a number divisible by 5) = (๐๐๐ก๐๐ ๐๐ข๐๐๐๐ ๐๐ ๐๐๐ ๐๐ ๐ค๐๐กโ ๐๐ข๐๐๐๐๐ ๐๐๐ฃ๐๐ ๐๐๐๐ ๐๐ฆ 5)/(๐๐๐ก๐๐ ๐๐ข๐๐๐๐ ๐๐ ๐๐๐ ๐๐ ) = 18/90 = ๐/๐