What is the value...?

[LMK27]

What is the easiest way to solve this?

If a + b = 9, what is the value of ab?

(1) a - b = 5

(2) b - a = -5


Statement (1) ALONE is sufficient, but statement (2) alone is insufficient.

Statement (2) ALONE is sufficient, but statement (1) is insufficient.

BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

EACH statement ALONE is sufficient.

Statements (1) and (2) TOGETHER are NOT sufficient.

Ans D

[papgust]

The easiest way is to just determine whether the equations could be solved simultaneously.

You have an equation with 2 unknowns in the question. To determine a and b, we need another equation to simultaneously determine a and b.

The 2nd equation with the same 2 unknowns are provided in Statement I and II. So, both are sufficient.

Remember. We just need to determine whether it's solvable in Data sufficiency questions. Here, we know that from 2 equations and 2 unknowns, we can determine the values of 2 unknowns. So, just knowing this itself is sufficient to answer.