Question

2. If 31z5 is a multiple of 9. where z is a digit, what is the value of
You will find that there are two answers for the last problem. Why is this so?
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Answer 1

Answer:

If a number is a multiple of 9, the sum of digits will be divisible by 9.

So 3+1+z+5 is a multiple of 9.

9+z is a multiple of 9 and z is a one digit number.

So z can be 0 and 9.

9+9=18 and 9+0=9 is a multiple of 9.

Answer 2

Answer:

z = 0 & 9

Step-by-step explanation:

RULES:

For any number to be divided by 9, the sum of each digit of that number should be divided by 9.

here,

sum of digit in 31z5 is :

3 + 1 + z + 5 = (9 + z)

So, (9 + z) /9 = 1 + (z/9)

here, z should be either 0 or multiple of 9.

but it can't be of 2 digit.

Hence, z = 0 and 9

Answered by GauthMath.