Data Sufficiency Decision Method Banking Quant

Why This Chapter Matters

Data sufficiency tests decision quality more than arithmetic stamina. The winning habit is to stop the moment sufficiency is established.

Do not solve more than the question asks. You only need to decide whether the statements are enough.
Check Statement I alone, then Statement II alone, then combine them only if needed.
Use standard answer patterns consistently to avoid avoidable mistakes.
Universal mathematical truths are allowed; outside factual knowledge is not.
Sufficiency depends on uniqueness. A statement that gives two possible answers is still insufficient.
A statement can be mathematically rich and still insufficient if it does not answer the exact question asked.

Concept	Formula / Rule
Standard coding A	Statement I alone is sufficient
Standard coding B	Statement II alone is sufficient
Standard coding C	Both together are sufficient, neither alone
Standard coding D	Either statement alone is sufficient
Standard coding E	Even both statements together are insufficient

Read the question target carefully.
Test Statement I without assuming anything extra.
Test Statement II independently.
Combine only if both alone fail but together may work.
Use elimination once one statement is clearly sufficient or clearly insufficient.
Check whether the question needs a value, a yes/no answer, or only a comparison direction.

Prompt: To find a unique value of a variable, a single linear equation in one variable is usually sufficient.

Approach: This type of structural observation often lets you decide sufficiency without calculating the final number.

Prompt: To find a boat’s still-water speed, knowing only one downstream speed is usually not enough unless you also know the stream relation.

Approach: This is a classic data-sufficiency habit: identify the missing variable instead of rushing into arithmetic.

Prompt: If the question asks "Is the number prime?" then a statement showing only that the number is odd is not sufficient.

Approach: Odd numbers can be prime or composite. The statement sounds useful, but it does not settle the target question.

Using hidden assumptions not supplied in the statements.
Combining statements too early.
Solving completely when uniqueness or inequality direction is already clear.
Ignoring the standard answer code and selecting the mathematical result instead.
Treating a yes/no question like a value question and demanding more information than needed.

The chapter is about control: test, stop, and classify.