Steps in Solving Reasoning Question
1) Get an overview: Read carefully the introduction and rules, to establish the cast of characters, the action and the number limit governing the problem.
2) Visualize and map out the problem: Make a mental picture of the problem and let it guide you to as you create a sketch or some other kind of scratch work, if need to help you to keep track of rules and handle new information.
3) Consider the rules individually: After you’ve thought through the meaning and implication of each rule, you have three choices:
a) Build it directly into sketch of your problem situation.
b) Jot down the rule in shorthand form to help you remember it.
c) Underline or circle those rules, which don’t lend themselves to the first two techniques.
4) Combine the rules: Look for common elements among the rules; that’s what will lead you to make deductions. Treat these deductions as additional rules, good for the whole exercise.
5) Work on the questions systematically: Read the question stem carefully! Take special notice of such words as must, could, cannot, not, impossible and except. As always, use the hypothetical information offered in ifclauses to set off a chain of deductions.
Illustration
Illustration:
Five mechanics Manu, Damu, Ramu, Somu and Ballu are assigned shifts to repair appliances on five days of a single week, Monday to Friday. There are exactly three shifts available to each mechanic each day a morning shift, an afternoon shift, and an evening shift. No more then one mechanic works for more then one shift in a single day.
 Exactly two mechanics work on each day of the week.
 Manu and Ballu work a shift on the same days of the week.
 Damu doesn’t work on any afternoon or evening shifts during the week.
 Ballu doesn’t work on any morning or afternoon shifts during the week.
 Manu works shifts on two consecutive days of the week.
 Somu’s second shift of the week is on an earlier day of the week then Manu’s first shift.
Q1 Which one of the following must be true?
A) Somu works a shift on Tuesday afternoon.
B) Damu works a shift on Monday morning.
C) Ballu works a shift on Thursday evening.
D) Ramu works a shift on Friday afternoon.
E) Manu works a shift on Tuesday morning.
Q2 If Ballu does not work a shift on Friday, which one of the following could be possible?
A) Ramu works a shift on Friday.
B) Somu works a shift on Tuesday.
C) Manu works a shift on Wednesday.
D) Somu works a shift on Monday.
E) Damu works a shift on Tuesday.
Steps
Step1: Get an overview
We need to schedule five mechanics, abbreviated M, D, R, S and B. in particular order during a five day calendar week, Monday to Friday. Be careful about the numbers governing this problem. There are supposed to be exactly two mechanics per day (never working on the same shift). Each mechanic must work exactly two shifts, and because mechanics are forbidden to take two shifts in the same day, this means that each mechanic will work on exactly two days. So, in effect, 10 out of the 15 available shifts will be taken, and five will be left untouched.
Step 2
Visualize and Map out the Problem
Go with whatever you feel is the most efficient way to keep track of the situation. Most people would settle on a sketch of the five days, each broken up in three shifts:

M 
T 
W 
Th 
F 
Morning 





Afternoon 





Evening 





Into this sketch one letter per box each entity will have to go twice (each mechanic does two shifts). So your pool of entities place would be: MMDDRRSSBB. You might want to add five Xs for the five shifts that won’t be taken by any of the mechanics.
Step 3
Consider the rules individually.
Consider this statement from introduction:
“No more than one mechanic works in any given shift”.
Make sure you interpret this rule correctly. You may have to paraphrase, in your own words, its exact meaning. In this case: two mechanics per shift is no good, three is out of the question, etc. but it doesn’t mean to imply that any given shift must have a repair person. If the test makers meant to imply that, they would have written, “Exactly one mechanic works on every given shift.” Notice the difference in wording. It’s subtle, but has a huge impact in solving problem.
Step 4
Combine the rules
This is the crucial phase in solving the problem. Here, notice that Manu appears in three of the six intended rules; that’s a good indication that combining these rules should lead somewhere useful. Combining Rule 2 and Rule 5 gives us two Manu/Ballu days in row. Ballu must be scheduled for evening shifts (remember we turned rule 4 into this positive statement.) That means that Manu would take the morning or afternoon shift on these consecutive days. Rule 6 concerns Manu as well; two Somus before two Manus. How is this possible? We need two Ss on different days to come before the two consecutive Ms. If Somu’s shifts are as early in the week as possible, she’ll work on Monday and Tuesday. That means that the earliest day that Manu can work (and Ballu as well, acc. to rule 2) is Wednesday. There’s our first really key deduction:
“Manu and Ballu cannot work on Monday and Tuesday; they must work on Wednesday, Thursday or Friday.” By further relating this deduction to Rule 5, it becomes clear that Manu and Ballu must work on Wednesday and Thursday or on Thursday or Friday. This brings us to another big deduction:
“Either way, Manu and Ballu must work on Thursday. According to rule 4, we can slot Ballu in for Thursday evening. Manu will then take Thursday morning or afternoon. The other Manu/Ballu day must be either Wednesday or Friday, to remain consecutive.”
Now that we’ve combined rules, and even have uncovered a few big deductions, it’s time to move on to the questions.
Step 5
Work the Questions Systematically:
Now you’ll see how all the work we did upfront pays off.
Q1 offers no hypothetical information; it simply asks what must be true. And as we have already deduced a few things that must be true, we can scan the choices for one that matches any one of our newly discovered pieces of information. It doesn’t take long to spot choice (C)  which is our big deduction clearly visible. You shouldn’t waste time in even checking other choices. Instead, have the confidence that you’ve done the right work the right way, and darken choice (C) and move on.
Q2 contains a hypothetical: no Ballu on Friday. One glance at our sketch tells us that the second Manu/ Ballu cluster must therefore be placed on Wednesday, next to Thursday Manu/ Ballu group. Somu must then work on Monday and Tuesday, in order to satisfy Rule 6 (although we don’t yet know the exact shifts he takes during those days).
That brings us to the two questions that test setters ask all too infrequently, “Who’s left?” and more importantly, “Where can they go?” Two D’s and Two R’s are left to place, with One spot on Monday, One spot on Tuesday and Two spots on Friday open to place them. How can this be done? Friday can’t get both D’s and both R’s (from the last sentence in introduction), so it will have to get one of each, with D in the morning and R in either the afternoon or evening. The other D and the other R will join S on Monday or Tuesday, in either order. Of course, whichever day D is on, he must be in the morning, whereas the exact shifts for R and S are ambiguous.
Look at how far the chain of deductions takes us, beginning with the simple statement in the question stem.
If Ballu doesn’t work a shift on Friday then………
With all of this information at our disposal, there’s not a question in the world that we can’t answer correctly. This one asks for a statement that could be false –which means that the four wrong choices will all be things that must be true. And in fact, choices A through D match the situation in the question perfectly, while E merely could be true: Damu’s first shift of the week could be on Tuesday, but it just as easily could be on Monday as well. (His second shift must be on Friday, of course.) E therefore is the only choice that could be false.