Help with this MC Q plz (1 Viewer)

[Swalbs]

An increase in investment expenditure of $100m changes the equilibrium level of
national income by $250m. What is the size of the Marginal Propensity to Consume?
(A) 0.4
(B) 0.6
(C) 1.25
(D) 2.50

I thought it was just 100/250 = 0.4, but the answer is 0.6 ?!
Im sure theres a simple answer, but im stumped, and even my teacher didnt get it. Question taken from the 2004 HSC

 

[sunjet]

When you divide (100/250) you get the MPS as the formula is 1/MPS then just 1 - MPS to get MPC.

Your teacher musn't be very good

 

[Swalbs]

When you divide (100/250) you get the MPS as the formula is 1/MPS then just 1 - MPS to get MPC.

Your teacher musn't be very good

But investment is an injection, which is part of consumption, so 100/250 should give the MPC

 

[sunjet]

No, it's the multiplier effect.

Investment (Injection) = $100m multiplied by multiplier to find increase in national Y.

250 = 100 x k
250 = 100 x 1 / mps
100 / MPS = 250
MPS = 100 / 250
MPS = 0.4
MPC = 1 - MPS
MPC = 1 - 0.4
MPC = 0.6

 

[Swalbs]

K i got the answer this way:
k = 250/100 = 2.5
Therefor 2.5 = 1/(1-MPC)
2.5 - 2.5MPC = 1
2.5MPC = 1.5
MPC = 1.5/2.5
= 0.6

This is just a variation of what you did. Thanks a lot for the help, ill be sure to show my teacher!