2016 CSAT, all questions
UPSC Prelims 2016 · CSAT
Question 39: Basic Numeracy
A piece of tin is in the form of a rectangle having length 12 cm and width 8 cm. This is used to construct a closed cube. The side of the cube is :
a2 cm
b3 cm
c4 cm
d6 cm
AnswerUPSC’s answer is (c).
A closed cube has 6 equal faces, so the tin's area equals 6 a^2, where a is the side. Area of the tin = 12 x 8 = 96 cm^2, so a^2 = 96 / 6 = 16 and a = 4 cm. Remember: the surface area of a closed cube is 6 times the square of its side, and the tin is used fully.
Why each option is right or wrong
- (a) A side of 2 cm needs only 24 cm^2.
- (b) A side of 3 cm needs only 54 cm^2.
- (c) Right: a side of 4 cm needs 96 cm^2.
- (d) A side of 6 cm needs 216 cm^2.
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.