Explain that sum total of APC and APS is equal to 1

Answer :

We know that: APC = C / Y  and APS = S / Y

We also know that:

Y = C + S (income is either consumed or saved)

(Dividing both sides of the equation by Y)

Y / Y = C / Y + S / Y

1 = APC + APS

So that,

APC + APS = 1

Or, APC = 1 – APS

Or, APS = 1 – APC