The same force will give a mass of 3M an acceleration of what?

Question

A force of F newtons will give an object with a mass of M an acceleration of A. The same force will give a mass of 3 M an acceleration of:

Multiple choice:
a) 1/3 A
b) 3 A
c) A
d) 1/9 A

I know the answer is a)1/3 A.
But, how do I show that.. please help me show work please

Answer 1

Or...

 

F=MA and the same force is F=(3M)A'

 

So we can set the forces equal to each other, MA = (3M)A'

 

Divide both sides by (3M) to achieve:

 

MA/(3M) = A' 

 

The masses cancel and we are left with.

 

(1/3)A = A'

Answer 2

F = MA

let primed values be new values

F' = F 

M' = 3M

F' = M'(A')  = 3M(A') = F = MA

then A' = MA/3M = A/3