The current ratio of a firm is $2:1$. What will be the impact of purchasing goods on credit on this ratio?

Let's assume initial values that give a current ratio of $2:1$:
$$\text{Current Assets (CA)}=2,00,000,\text{Current Liabilities (CL)}=1,00,000$$
If goods worth $\text{Rs. }50,000$ are purchased on credit:Inventory (Current Asset) increases by $50,000\to \text{New CA}=2,50,000$ Creditors (Current Liability) increases by $50,000\to \text{New CL}=1,50,000$ Now, calculate the new ratio:
$$\text{New Current Ratio}=\frac{2,50,000}{1,50,000}\approx 1.67:1$$
Since $1.67:1$ is less than $2:1$, the purchase of goods on credit will decrease the ratio.