UPSC Prelims 2009 · General Studies
Question 107: Logical Reasoning and Mental Ability
There are three cans A, B and C. The capacities of A, B and C are 6 litres, 10 litres and 16 litres respectively. The can C contains 16 litres of milk. The milk has to be divided in them using these three cans only. Consider the following statements :
- 1.It is possible to have 6 litres of milk each in can A and can B.
- 2.It is possible to have 8 litres of milk each in can B and can C.
Which of the statements given above is/are correct ?
AnswerThe answer is (c).
Both are possible. For 6 and 6: pour C into A (6,0,10), A into B (0,6,10), C into A (6,6,4). For 8 and 8: pour C into B (0,10,6), B into A (6,4,6), A into C (0,4,12), B into A (4,0,12), C into B (4,10,2), B into A (6,8,2), A into C (0,8,8). Each triple shows cans A, B and C.
- 1. Pours reach A = 6, B = 6, C = 4.
- 2. Pours reach A = 0, B = 8, C = 8.
How you could have got this
- If you were sure statement 1 is correct, (b) and (d) go: each of them leaves 1 out.
What you needed to know: Pours reach A = 6, B = 6, C = 4.
- Then, if you were sure statement 2 is correct, (a) goes: it leaves 2 out.
What you needed to know: Pours reach A = 0, B = 8, C = 8.
Only (c) is left. This one needs every statement.
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) Wrong: statement 2 is also possible.
- (b) Wrong: statement 1 is also possible.
- (c) Right: both divisions can be made.
- (d) Wrong: both divisions can be made.
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.