Functions - one-one, into and onto — practice questions

Question 1 · difficulty L3 · understanding

Let $\mathrm{A}=\{1,2,3,4,5,6\}$. The number of one-one functions $f: \mathrm{A} \rightarrow \mathrm{A}$ such that $f(1) \geq 3, f(3) \leq 4$ and $f(2)+f(3)=5$, is $\_\_\_\_$ .

Question 2 · difficulty L3 · understanding

Let $$A=\{(x, y): 2 x+3 y=23, x, y \in \mathbb{N}\}$$ and $$B=\{x:(x, y) \in A\}$$. Then the number of one-one functions from $$A$$ to $$B$$ is equal to _________.

Question 3 · difficulty L3 · understanding

Let $$\mathrm{A}=\{1,2,3, \ldots, 7\}$$ and let $$\mathrm{P}(\mathrm{A})$$ denote the power set of $$\mathrm{A}$$. If the number of functions $$f: \mathrm{A} \rightarrow \mathrm{P}(\mathrm{A})$$ such that $$\mathrm{a} \in f(\mathrm{a}), \forall \mathrm{a} \in \mathrm{A}$$ is $$\mathrm{m}^{\mathrm{n}}, \mathrm{m}$$ and $$\mathrm{n} \in \mathrm{N}$$ and $$\mathrm{m}$$ is least, then $$\mathrm{m}+\mathrm{n}$$ is equal to _________.

Question 4 · difficulty L3 · understanding

Let $$\mathrm{A}=\{1,2,3,4,5\}$$ and $$\mathrm{B}=\{1,2,3,4,5,6\}$$. Then the number of functions $$f: \mathrm{A} \rightarrow \mathrm{B}$$ satisfying $$f(1)+f(2)=f(4)-1$$ is equal to __________.

Question 5 · difficulty L3 · understanding

Let $$\mathrm{R}=\{\mathrm{a}, \mathrm{b}, \mathrm{c}, \mathrm{d}, \mathrm{e}\}$$ and $$\mathrm{S}=\{1,2,3,4\}$$. Total number of onto functions $$f: \mathrm{R} \rightarrow \mathrm{S}$$ such that $$f(\mathrm{a}) \neq 1$$, is equal to ______________.

Question 6 · difficulty L3 · understanding

The number of functions $$f$$, from the set $$\mathrm{A}=\left\{x \in \mathbf{N}: x^{2}-10 x+9 \leq 0\right\}$$ to the set $$\mathrm{B}=\left\{\mathrm{n}^{2}: \mathrm{n} \in \mathbf{N}\right\}$$ such that $$f(x) \leq(x-3)^{2}+1$$, for every $$x \in \mathrm{A}$$, is ___________.

Question 7 · difficulty L3 · understanding

Let A = {0, 1, 2, 3, 4, 5, 6, 7}. Then the number of bijective functions f : A $$\to$$ A such that f(1) + f(2) = 3 $$-$$ f(3) is equal to

Question 8 · difficulty L3 · understanding

Let $f: \mathbf{R} \rightarrow \mathbf{R}$ be defined as $f(x)=\frac{2 x^2-3 x+2}{3 x^2+x+3}$. Then $f$ is :

• A. both one-one and onto
• B. one-one but not onto
• C. onto but not one-one
• D. neither one-one nor onto

Question 9 · difficulty L3 · understanding

The number of functions $f:\{1,2,3,4\} \rightarrow\{a, b, c\}$, which are not onto, is :

• A. 48
• B. 45
• C. 51
• D. 35

Question 10 · difficulty L3 · understanding

Given below are two statements : Statement I : The function $f: \mathbb{R} \to \mathbb{R}$ defined by $f(x) = \frac{x}{1 + |x|}$ is one-one. Statement II : The function $f: \mathbb{R} \to \mathbb{R}$ defined by $f(x) = \frac{x^2 + 4x - 30}{x^2 - 8x + 18}$ is many-one. In the light of the above statements, choose the correct answer from the options given below :

• A. Statement I is true but Statement II is false
• B. Both Statement I and Statement II are false
• C. Both Statement I and Statement II are true
• D. Statement I is false but Statement II is true