REPEATED ARRANGEMENTS AND SERIES QUESTIONS
REPEATED ARRANGEMENTS AND SERIES QUESTIONS 1. If all the numbers between 11 and 100 are written on a piece of paper. How many times will the number 4 be used? a.19 b.21 c.34 d.22 Answer: a Explanation: We have to consider the number of 4’s in two-digit numbers. _ _ If we fix 4 in the 10th place, the unit place is filled with 10 ways. If we fix 4 in units place, 10th place be filled with 9 ways (0 is not allowed) So a total of 19 ways. Alternatively: There are total 9 4’s in 14, 24, 34…,94 & total 10 4’s in 40,41,42….49 thus, 9+10=19. 2. 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4…… In the above sequence what is the number of the position 2888 of the sequence. a) 1 b) 4 c) 3 d) 2 Answer: c Explaination: First if we count 1223334444. they are 10 In the next term they are 20 Next they are 30 and so on So Using n(n+1)2×10 ≤ 2888 For n = 23 we get LHS as 2760. Remaini...