Question

If $A=\{a,b\},B=\{1,2,3\}$, find B $\times$ A

• A. $B$ $\times$ $A$$=\left\{\right(1,a),(2,a),(3,a),(1,b\left)\right(2,b),(3,b\left)\right\}$
• B. $B$ $\times$ $A$$=\left\{\right(2,a),(3,a),(1,b\left)\right(2,b),(3,b\left)\right\}$
• C. $B$ $\times$ $A$$=\left\{\right(1,a),(2,a),(3,a),(1,b\left)\right(2,b\left)\right\}$
• D. None of these

Answer 1

The correct option is A $B$ $\times$ $A$$=\left\{\right(1,a),(2,a),(3,a),(1,b\left)\right(2,b),(3,b\left)\right\}$

To find B × A multiply each element of B with that of A & form an ordered pair.

i.e. ordered pairs are (1,a); (2,a); (3,a); (1,b); (2,b); (3,b)

Therefore B × A = { (1,a), (2,a), (3,a), (1,b), (2,b), (3,b)}