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There are n sisters in a family. They each have one dress. They decide to exchange their dresses such that nobody wears her own dress. They try all such combinations and take pictures. All the sisters appear in each picture and the order in which they appear does not count. Each possible way of dressing is photographed exactly once. If there are 44 such pictures, what is the value of n ?
Consider the three couples in Chintu, Pintu and Mintu and their wives Chinky, Pinky and Minky. After the dinner party, one more couple Rinku and Rinki arrives to meet them and they all decide to dance. They all want to dance in pairs where each pair consists of a man and a woman. In how many ways can such pairs be formed if nobody can have their spouse as a partner? (For example, one possible way is: Chintu & Rinky, Pinku & Chinky, Mintu & Pinky, Rinku & Minky.)

Prove that 2^(n+1) > (n + 2) · sin(n) for all positive integers n



(3). If p, q, and r denote the following propositions:

p : 2 < 3.

q : The cube of -1 is -1.

r : The empty set contains one element.


express the following propositions symbolically.


(a) If 2 ≥ 3, then the cube of -1 is -1.


(b) If and only if 2 < 3 or the cube of -1 is not -1 then the empty

set does not contain one element.


(c) The empty set contains one element and, if 2 ≥ 3, then the

cube of -1 is -1.



What is the big-O estimate of the function given in the pseudocode below if the size of the input is n? (a function that takes in a list of numbers as input and returns the biggest number) Justify your answer.


define function(input_list):

for i from range 0 to length(input_list):

min_idx = i

for j from range item+1 to length(input_list):

if input_list[min_idx] > input_list[j]:

min_idx = j

input_list[i], input_list[min_idx] = input_list[min_idx], input_list[i]

return input_list[length(input_list)]



Solve for x if (g ◦ f)(x) = 1. Here, f(x) = (xlog(x) · x2) and g(x) = log(x) + 1.



Find the big−O, big−Ω estimate for x7y3+x5y5+x3y7. [Hint: Big-O, big- Ω, and big-Θ notation can be extended to functions in more than one variable. For example, the statement f(x, y) is O(g(x, y)) means that there exist constants C, k1, and k2 such that |f(x, y)| ≤ C|g(x, y)| whenever x > k1 and y > k2.]



Consider the function f(n) = 35n3+ 2n3log(n) − 2n2log(n2) which represents the complexity of some algorithm.

(a) Find a tight big-O bound of the form g(n) = np for the given function f with some natural number p. What are the constants C and k from the big-O definition?

(b) Find a tight big-Ω bound of the form g(n) = np for the given function f with some natural number p. What are the constants C and k from the big- Ω definition?

(c) Can we conclude that f is big−Θ (np) for some natural number p?



Find a div b and a mod b when:

(a) a = 30303, b = 333

(b) a = −765432, b = 38271



Show that if n | m, where n and m are integers greater than 1, and if a≡b (mod m), where a and b are integers, then a≡b (mod n).




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