Question

For any natural n,the digital root of 7n cannot be.

Answer 1

Answer:

A Perfect cube Number

Step-by-step explanation:

Digital root is sum of numbers. So, Digital Root of 356 is 5.

3 + 5 + 6 = 14 -> 1 + 4 = 5

Now, as per properties of Digital Root, for a perfect cube number digital root will be  1,8 or 9. We will never have 7 here.

Consider some examples :-

729 (Perfect Cube of 9) = 7 + 2 + 9 = 18 -> 1 + 8 -> 9

So digital cube of 729 - 9

Similarly, digital root of other perfect cube numbers are as follows:-

1 (Perfect Cube of 4) -> 1

8 (Perfect Cube of 2) -> 8

27 (Perfect Cube of 3) -> 9

64 (Perfect Cube of 4) -> 1

125 (Perfect Cube of 5) -> 8

216 (Perfect Cube of 6) -> 9

You will never find 7 here as digital root.

So natural number n if it has a digital root of 7, it will never be perfect cube number.

Answer 2

Step-by-step explanation:

for any natural number 'n' the number 7n cannot end with the digit