What is the largest multiple of 9 which is smaller than - 70?

Step-by-step explanation:

Let's say the number "n" were the largest multiple of 9. But then:

Consider n + 9. n is itself a multiple of 9, so n = 9k, so n + 9 = 9 (k + 1), so n + 9 is also a multiple of 9, and n + 9 is larger than n.

So there can't be a largest multiple of 9 (or any number).

Answer: The number is - 72

Step-by-step explanation:

We want the largest multiple of 9 (this is a number equal to 9*r, where r is a real number) that is smaller than - 70

So we want the first multiple of 9 that is smaller than - 70.

We have that 9*8 = 72

so we will also have that 9*-8 = - 72

now, - 72 is smaller than - 70

-72 is a multiple of 9.

-72 is the first multiple of 9 smaller than - 70 (the next is 9¨-9 = - 81) so we have that - 72 is the largest multiple of 9 that is also smaller than - 70.