Question

Indicate the number divisible by 3 and 5 simultaneously

a) 715
b)220
c)255
d)369

Answer 1

c) 255.

Explanation:

You need a number whose last digit is 0 or 5 and is divisible by 3.

So first of all the number can;'t be 369.

A quick way to see if a number is divisible by 3 is to add all its digits until you get a single digit. Then if this digit is 3, 6 or 9 then the number is divisible by 3,

So in the case of 255 we have:

2+ 5+ 5 = 12 , 1 + 2 = 3.

We see that 220 and 715 produce digits 4 and 7+1+5 = 13 = 4 so it cant be one of them

Answer 2

c) 255

Explanation:

d isn't divisible by 5 and both a and b aren't divisible by 3