Closer than most people guess: Mongolia (1,560,428 km² km²) is only about 20%% larger than Peru (1,296,279 km² km²).
Mongolia sits in Asia, Peru in South America. 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 Mongolia about 2.2× and Peru about 1×, so on a Mercator-style map this pair appears 2.5× apart instead of the true 1.2×.
Peru fits 1× into Mongolia.