JEE Main 2022 · 25 Jul · Shift 1 · Mathematics Q1

MathematicsSingle correct+4 / -1Question 1 of 90

The total number of functions, $f:\{1,2,3,4\}\to\{1,2,3,4,5,6\}$ such that $f(1)+f(2)=f(3)$ , is equal to :

108

126

Answer and worked solution

Official answer: B

Count triples. $f(3)=f(1)+f(2)\le6$ : pairs with sum at most 6 number $1+2+3+4+5=15$ . $f(4)$ is free: $15\times6=90$ .

(B)

Topics:Types of functions Fundamental principle of counting

JEE Main 2022 · 25 Jul · Shift 1, Mathematics question 1