Closer than most people guess: Argentina (2,782,703 km² km²) is only about 19%% larger than Democratic Republic of the Congo (2,334,703 km² km²).
Argentina sits in South America, Democratic Republic of the Congo in Africa. On the old Mercator map the latitude gap distorted how large each felt beside the other; at true size the answer is simply 1.2×.
The old map muddied it further: Mercator inflates Argentina about 1.5× and Democratic Republic of the Congo about 1×, so on a Mercator-style map this pair appears 1.8× apart instead of the true 1.2×.
Democratic Republic of the Congo fits 1× into Argentina.