There are different topics which can be asked in Data Sufficiency.
- Blood Relation
- Inequality/Mathematical Operator
- Sitting Arrangement
- Ranking & Direction
- Coding-Decoding
Here are some basic tips to get you on track:
No excuses: On Data Sufficiency, they’re always the same! Know in the blink of an eye what choice C is. On test day, if you find that Statement 1 is insufficient, be able to cross out choices A and D without hesitation.
- Write down what you absolutely need in order to find certain quantities.
Each statement alone will be sufficient if both of the statements on their own contain all the information necessary to answer the question. The statements will be sufficient together if they contain every piece of necessary information between them. Take the area of a parallelogram: Do you need to know every side length to determine the area? If you have every side length, can you find the area?
- Don’t look at the statements together.
Statement 2 may tell you that x is negative, but that fact has no bearing on Statement 1 when viewed by itself. Explore all the possibilities offered by each statement individually. If you’ve scrutinized Statement 1 and found it sufficient, be equally merciless when it comes to Statement 2.
- Important information is often buried in the prompt.
Don’t pay so much attention to the statements that you forget the rest of the question. Often, half the information that you need is in the set-up.
- Know when it’s actually necessary to solve single-variable equations.
If the question asks for the value of z and you whittle the problem down to an equation like 30z = 2(500) – 925, don’t waste your time solving for z! It’s only important to know that you COULD solve if you wanted to. Remember, all linear one-variable equations have a unique solution, but quadratic equations—equations with an x^2 term—can have zero, one, or two solutions.
- Know when it’s necessary to solve a system of equations.
Again, you never need to solve a DS problem—you only need to know that you could. A system of n independent linear equations with n variables can be solved for ALL of the n variables. The key word here is “independent”: Equations are independent if they’re not multiples of one another. For example, y = 2x and 3y = 6x are NOT independent equations because the second equation is just three times the first. If on test day you don’t feel comfortable declaring that a system of equations is solvable, get the system down to one single-variable equation and then reassess.
- Study prime factorizations and divisibility.
If x is divisible by 15, will x^2 be divisible by 27? What about x^3?
- Study overlapping sets.
Be comfortable representing these overlapping sets with Venn diagrams. This topic is a DS favorite. A statement like, “The number of widgets that were not made in Factory A or Factory B is three times greater than the number of widgets that were made in Factory B” can be difficult to unpack in the heat of the moment. Train yourself to answer questions about sets methodically and quickly.
- Remember that only 2 out of the 5 answer choices involve looking at both statements together.
This means that there’s a 60% chance that the correct answer will treat the statements on an individual footing. It can be tempting to use all the information the problem provides, but keep these odds in mind. Choices C and E, as a group, are 20% less likely to be correct than choices A, B, and D, as a group.
- Be on the lookout for statements that give no new information.
The area of a square, for instance, contains just as much information as the side length of the square. If you know the area, you can find the side length; conversely, if you know the side length, you can find the area. Often on the DS section, Statement 2 will just be a repackaging of the same information provided by Statement 1.
Questions & Answers
In each of the questions below consists of a question and two statements numbered I and II given below it. You have to decide whether the data provided in the statements are sufficient to answer the question. Read both the statements and give answer
(A) If the data in statement I alone are sufficient to answer the question, while the data in statement II alone are not sufficient to answer the question
(B) If the data in statement II alone are sufficient to answer the question, while the data in statement I alone are not sufficient to answer the question
(C) If the data either in statement I alone or in statement II alone are sufficient to answer the question
(D) If the data given in both statements I and II together are not sufficient to answer the question and
(E) If the data in both statements I and II together are necessary to answer the question.
1: How much was the total sale of the company?
Statements:
I- The company sold 8000 units of product A each costing Rs. 25.
II- This company has no other product line.
A) I alone is sufficient while II alone is not sufficient
B) II alone is sufficient while I alone is not sufficient
C) Either I or II is sufficient
D) Neither I nor II is sufficient
E) Both I and II are sufficient
Solution- We can find the value of total sale of the company from statement 1 only. Total cost =8000X25=200000 Rs.
From 2nd statement we know that the company deals only in product A, because it is given that company has no other product line.
So Answer is E (Both Statements are sufficient)
2. What will be the total weight of 10 poles, each of the same weight?
Statements:
I- One-fourth of the weight of each pole is 5 kg.
II- The total weight of three poles is 20 kilograms more than the total weight of two poles.
A) I alone is sufficient while II alone is not sufficient
B) II alone is sufficient while I alone is not sufficient
C) Either I or II is sufficient
D) Neither I nor II is sufficient
E) Both I and II are sufficient
Solution- From 1st statement, it is given that one fourth of the weight of each pole is 5 kg., so weight of total pole is 20 kg.(5X4), Hence we can find the weight of 10 poles, which is 20X10=200 kg.
From 2nd statement it is give that Total weight of three poles is 20 kg more than the total weight of two poles.
Weight of each pole = (weight of 3 poles) - (weight of 2 poles) = 20 kg.
So, total weight of 10 poles = (20 x 10) kg = 200 kg.
Answer is C ( Either I or II statement is sufficient)
Now try to solve problems from book. If you have any query regarding this topic, feel free to ask. :-)
