In a group of 120 persons, 80 are Indians and rest are foreigners. Further, 70 persons in the group can speak English. The number of Indians who can speak English is

(a) 20
(b) 30
(c) 30 or less
(d) 30 or more ✓ UPSC's answer

Why the answer is (d)

• Total persons = 120; Indians = 80, so foreigners = 120 - 80 = 40.

• Total English speakers = 70; let Indian English speakers = x and foreign English speakers = y, so x + y = 70.

• Since only 40 foreigners exist, y cannot exceed 40.

• Therefore x = 70 - y is at least 70 - 40 = 30.

• Hence the number of Indians who can speak English must be 30 or more, so option (d) follows.

Why the other options are wrong

(a) 20: 20 is impossible because even if all 40 foreigners speak English, 70 - 40 = 30 Indians must speak English.
(b) 30: 30 is only the minimum possible value, not the exact number, because the number can be higher if fewer foreigners speak English.
(c) 30 or less: 30 or less is wrong because the minimum is 30 and the value can be greater than 30.

Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2021, held on 10 October 2021. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.