WBJEE · Maths · Functions
The total number of injections (one-one into mappings) from \(\quad\left\{a_{1}, a_{2}, a_{3}, a_{4}\right\}\)
\(\left(b_{1}, b_{2}, b_{3}, b_{4}, b_{5}, b_{6}, b_{7}\right)\) is
- A 400
- B 420
- C 800
- D 840
Answer & Solution
Correct Answer
(D) 840
Step-by-step Solution
Detailed explanation
Let \(A=\left\{a_{1}, a_{2}, a_{3}, a_{4}\right\}\) \(\begin{aligned} B &=\left\{b_{1}, b_{2}, b_{3}, b_{4}, b_{5}, b_{6}, b_{7}\right\} \\ n(A) &=4, n(B)=7 \end{aligned}\) The total number of infections \(={ }^{7} P_{4}\) \(=\frac{71}{3 !}=7 \cdot 6 \cdot 5 \cdot 4=840\)
See the Complete Solution
Get step-by-step explanations for this and 2.5 Lakh+ more JEE, NEET & CET questions.
- Unlock all solutions
- Practice the full chapter
- Track accuracy across PYQs
4.8 rated on Google Play · 14,000+ reviews
More questions from Maths
- If \(y=\frac{A}{x}+B x^2\), then \(x^2 \frac{d^2 y}{d x^2}=\)WBJEE 2011 Medium
- \(f(x)=\left\{\begin{array}{cc}{[x]+[-x],} & \text { when } x \neq 2 \\ \lambda & \text { when } x=2\end{array}\right.\)
If \(f(x)\) is continuous at \(x=2\), the value of \(\lambda\) will beWBJEE 2011 Medium - For the two circles \(x^2+y^2=16\) and \(x^2+y^2-2 y=0\) there is / areWBJEE 2009 Hard
- If \(x+\frac{1}{x}=2 \cos \theta\), then for any integer \(n, x^n+\frac{1}{x^n}=\)WBJEE 2011 Hard
- Suppose that \(z_{1}, z_{2}, z_{3}\) are three vertices of an equilateral triangle in the angand plane. Let \(\alpha=\frac{1}{2}(\sqrt{3}+i)\) and \(\beta\) be a non-zero complex number. The points \(a z_{1}+\beta, \alpha z_{2}+\beta, \alpha z_{3}+\beta\) will beWBJEE 2014 Hard
- If \(a, b\) are odd integers, then the roots of the equation \(2 a x^2+(2 a+b) x+b=0, a \neq 0\) areWBJEE 2022 Medium
More PYQs from WBJEE
- The sum of \(n\) terms of the following series \(1^{3}+3^{3}+5^{3}+7^{3}+\ldots\) isWBJEE 2016 Medium
- \[
\text { The reading of the ammeter in the following figure will be }
\]
WBJEE 2010 Easy - \(\int_0^{1000} e^{x-[x]}\) is equal toWBJEE 2009 Hard
- Identify the correct statement.WBJEE 2013 Easy
- Amongst the following, which should have the highest rms speed at the same temperature?WBJEE 2016 Medium
- Which one of the following is called a carbylamine?WBJEE 2009 Easy