2009 General Studies, all questions
UPSC Prelims 2009 · General Studies
Question 101: Basic Numeracy
Four metal rods of lengths 78 cm, 104 cm, 117 cm and 169 cm are to be cut into parts of equal length. Each part must be as long as possible. What is the maximum number of pieces that can be cut?
a27
b36
c43
d480
AnswerThe answer is (b).
The longest equal piece is the highest common factor of 78, 104, 117 and 169. Since 78 = 6 x 13, 104 = 8 x 13, 117 = 9 x 13 and 169 = 13 x 13, the HCF is 13 cm. The pieces are 6 + 8 + 9 + 13 = 36.
Why each option is right or wrong
- (a) 27 is not the sum of the piece counts.
- (b) Right: 6 + 8 + 9 + 13 = 36 pieces of 13 cm.
- (c) 43 is not the sum of the piece counts.
- (d) 480 is far too many for a 13 cm cut.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2009, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.