TOP 20 NDA Maths Questions With Answer

Here is the best top 20 NDA Maths Questions Objective type which can help to improve in your preparation. Answer Key is also attached in the end.

Question 1. Let * be a binary operation on set Q – {1} defind by a * b = a + b – ab : a, b ∈ Q – {1}. Then * is

(a) Commutative (b) Associative (c) Both (a) and (b) (d) None of these

Question 2. The binary operation * defined on N by a * b = a + b + ab for all a, b ∈ N is

(a) commutative only (b) associative only (c) both commutative and associative (d) none of these

Question 3. The number of commutative binary operation that can be defined on a set of 2 elements is

(a) 8 (b) 6 (c) 4 (d) 2

Question 4. Let T be the set of all triangles in the Euclidean plane, and let a relation R on T be defined as aRb if a is congruent to b ∀ a, b ∈ T. Then R is

(a) reflexive but not transitive (b) transitive but not symmetric (c) equivalence (d) None of these

Question 5. The maximum number of equivalence relations on the set A = {1, 2, 3} are

(a) 1 (b) 2 (c) 3 (d) 5

Question 6. Let us define a relation R in R as aRb if a ≥ b. Then R is

(a) an equivalence relation (b) reflexive, transitive but not symmetric (c) symmetric, transitive but not reflexive (d) neither transitive nor reflexive but symmetric

Question 7. Let A = {1, 2, 3} and consider the relation R = {(1, 1), (2, 2), (3, 3), (1, 2), (2, 3), (1, 3)}. Then R is

(a) reflexive but not symmetric (b) reflexive but not transitive (c) symmetric and transitive (d) neither symmetric, nor transitive

Question 8. The identity element for the binary operation * defined on Q – {0} as a * b = ab2 ∀ a, b ∈ Q – {0) is

(a) 1 (b) 0 (c) 2 (d) None of these

Question 9. Let A = {1, 2, 3, …. n} and B = {a, b}. Then the number of surjections from A into B is

(a) nP2 (b) 2n – 2 (c) 2n – 1 (d) none of these

Question 10. Let f : R → R be defind by f(x) = 1x ∀ x ∈ R. Then f is

(a) one-one (b) onto (c) bijective (d) f is not defined

Question 11. Which of the following functions from Z into Z are bijective?

(a) f(x) = x3 (b) f(x) = x + 2 (c) f(x) = 2x + 1 (d) f(x) = x2 + 1

Question 12. Let f : R → R be the functions defined by f(x) = x3 + 5. Then f-1(x) is

(a) (x+5)13 (b) (x−5)13 (c) (5−x)13 (d) 5 – x

Question 13. Let f : R – {35} → R be defined by f(x) = 3x+25x−3. Then

(a) f-1(x) = f(x) (b) f-1(x) = -f(x) (c) (fof) x = -x (d) f-1(x) = 119 f(x)

Question 14. Let f : R → R be given by f(x) = tan x. Then f-1(1) is

(a) π4 (b) {nπ + π4; n ∈ Z} (c) Does not exist (d) None of these

Question 15. Let R be a relation on the set N of natural numbers denoted by nRm ⇔ n is a factor of m (i.e. n | m). Then, R is

(a) Reflexive and symmetric (b) Transitive and symmetric (c) Equivalence (d) Reflexive, transitive but not symmetric

Question 16. Let S = {1, 2, 3, 4, 5} and let A = S × S. Define the relation R on A as follows: (a, b) R (c, d) iff ad = cb. Then, R is

(a) reflexive only (b) Symmetric only (c) Transitive only (d) Equivalence relation

Question 17. Let R be the relation “is congruent to” on the set of all triangles in a plane is

(a) reflexive (b) symmetric (c) symmetric and reflexive (d) equivalence

Question 18. Total number of equivalence relations defined in the set S = {a, b, c} is

(a) 5 (b) 3! (c) 23 (d) 33

Question 19. The relation R is defined on the set of natural numbers as {(a, b) : a = 2b}. Then, R-1 is given by

(a) {(2, 1), (4, 2), (6, 3),….} (b) {(1, 2), (2, 4), (3, 6), ……..} (c) R-1 is not defiend (d) None of these

Question 20. Let X = {-1, 0, 1}, Y = {0, 2} and a function f : X → Y defiend by y = 2×4, is

(a) one-one onto (b) one-one into (c) many-one onto (d) many-one into  

TOP 20 NDA MATHS QUESTIONS  Answer Key: –