"The partial pressure is the pressure exerted...."
Explanation:
"The partial pressure is the pressure exerted by a component, A," "in a gaseous mixture. " P_A" is the same as the pressure it would""exert if it ALONE occupied the container."
And thus P_"total"=P_A+P_B+P_C.........
If we assume ideality, then P_"Total"=(n_"Total"RT)/V
=(n_1+n_2+n_3.....)xx(RT)/V
And thus the "partial pressure" is proportional to its molar quantity.