Question

7. Luis wants to send his grandpa a letter, but he has forgotten the postcode. He knows:
the postcode is a 5-digit number
the postcode begins with 68
all digits are different
• all digits are even (Recall that 0 is an even number.)
How many postcodes are there which satisfy these conditions?
a) 3
b) 6
c) 12
d) 18
e) 27

Answer 1

Răspuns:

b) 6

Explicație pas cu pas:

număr format din cinci cifre pare diferite, numărul începe cu 68

the postcode is a 5-digit number

the postcode begins with 68

$\overline {68abc} , \ a \neq b \neq,c$

all digits are different & all digits are even

$a,b,c \in \{0,2,4\}$

$\implies 3 \times 2 \times 1 = \bf 6$