UPSC Prelims 1998 · General Studies
Question 136: Basic Numeracy
Out of the three annual examinations, each with a total of 500 marks, a student secured average marks of 45 % and 55 % in the first and second annual examinations. To have an overall average of 60 %, how many marks does the student need to secure in the third annual examination?
AnswerThe answer is (b).
Three examinations of 500 marks make 1500 marks, and an overall average of 60 per cent needs 900 marks. The student scored 45 per cent of 500 = 225 and 55 per cent of 500 = 275, a total of 500. The third paper must give 900 - 500 = 400 marks.
How you could have got this
No shortcut here: in a “how many” question, ruling out options doesn’t help. Every statement has to be judged.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) 450 would give a total of 950, an average above 60 per cent.
- (b) Right: 225 + 275 + 400 = 900, or 60 per cent of 1500.
- (c) 350 would give a total of 850, below 60 per cent.
- (d) 300 would give a total of 800, below 60 per cent.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 1998, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.