April 1999
MA214: DISCRETE MATHEMATICS

QUESTION 1 (Compulsory)

Total Marks: 20 Marks

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SAMPLE STUDENT'S SOLUTIONS
for Question 1

 

(a) Let A be the null set.
(i) What is the cardinality of A? [1]
(ii) What is the cardinality of the power set P(A)? [1]
(iii) What is the cardinality of the power set P(P(A))? [1]
(iv) List the elements of the power set P(P(P(A))).

 

[1]
(b) Consider the following statement

" basketball players x, x is tall

Which of the following are equivalent ways of expressing this statement?

[2]
(i) Every basketball player is tall.
(ii) Some basketball players are tall.
(iii) Some of all tall people are basketball players.
(iv) Anyone who is tall is a basketball player.
(v) All people who are basketball players are tall

 

(c) (i) How many ways can the letters of the word DESIGN be arranged in a row? [1]
(ii) How many ways can the letters of the word DESIGN be arranged in a row if G and N must remain next to each other as either GN or NG?

 

[2]
(d) Given the matrices

 pic1.gif (871 bytes) ,
calculate the matrix (AB)t .

 

[3]
(e) Calculate the inverse of the function

    f(x) = 10 - 2x

 

[3]
(f) Prove by induction that n3 - n is divisible by 6 for n ³ 1. [5]