2,838 is divisible by
a. 3
b. 9
c. 4
explain your reasoning for your choice(s).

a

Step-by-step explanation:

a. a number is divisible by 3 if the sum of its dígits is divisible by 3

2+8+3+8=21

21 is divisible by 3 (3*7=21), then 2838 is divisible by 3 too.

b. a number is divisible by 9 if the sum of its dígits is divisible by 9

2+8+3+8=21

21 isn't divisible by 9 (2*9=18 and 3*9=27), then 2838 is not divisible by 9.

c. a number is divisible by 4 if the number formed by its too last dígits is divisible by 4.

38 isn't divisible by 4 (4*9=36 and 4*10=40), then 2838 is not divisible by 4.