UPSC Prelims 2016 · CSAT
Question 30: Basic Numeracy
Anita's mathematics test had 70 problems carrying equal marks i.e., 10 arithmetic, 30 algebra and 30 geometry. Although she answered 70% of the arithmetic, 40% of the algebra and 60% of the geometry problems correctly, she did not pass the test because she got less than 60% marks. The number of more questions she would have to answer correctly to earn a 60% passing marks is :
AnswerUPSC’s answer is (b).
Marks per problem are equal, so count problems. Correct: arithmetic 70% of 10 = 7, algebra 40% of 30 = 12, geometry 60% of 30 = 18, total 37. Passing needs 60% of 70 = 42. So she needs 42 - 37 = 5 more correct answers. Remember: with equal marks, work in problem counts rather than percentages.
Why each option is right or wrong
- (a) One more gives 38, below 42.
- (b) Right: 37 + 5 = 42, which is 60% of 70.
- (c) Seven more gives 44, more than needed.
- (d) Nine more gives 46, more than needed.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2016, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.