The investment multiplier can be Expressed as:

$\frac{ΔY}{ΔI}$

The correct answer is option (2) : $\frac{ΔY}{ΔI}$

The investment multiplier $\frac{ΔY}{ΔI}$ represents the change in the overall income Δ Y resulting from a change in investment ΔI

When there is an increase in investment ΔI, it leads to a multiplied effect on the total income Δ Y in the economy. The multiplier effect occurs because additional income as it ripples through the economy. This additional income, in turn, leads to further rounds of spending and income generation.