BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

What is the area of a right triangle?

Expert replies
by Max@Math Revolution » Mon Feb 11, 2019 1:14 am

Timer

00:00

Answers

A

B

C

D

E

Stats

Difficulty

[GMAT math practice question]

What is the area of a right triangle?

1) The length of one side is 3
2) The length of one side is 4
Join the discussion
Source: — Data Sufficiency |

by Brent@GMATPrepNow » Mon Feb 11, 2019 6:23 am
Max@Math Revolution wrote:[GMAT math practice question]

What is the area of a right triangle?

1) The length of one side is 3
2) The length of one side is 4
Target question: What is the area of a right triangle?

Statement 1: The length of one side is 3
Knowing the length of only 1 side will not help us answer the target question with certainty.
Statement 1 is NOT SUFFICIENT

Statement 2: The length of one side is 4
NOT SUFFICIENT (same reason as above)

Statements 1 and 2 combined
There are two possible triangles that satisfy BOTH statements. They are as follows:

Case a:
Image
In this case, the answer to the target question is the area = (4)(3)/2 = 6


Case b:
Image
In this case, the answer to the target question is the area = (√7)(3)/2 = 3√7/2
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Answer: E

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Join the discussion

by Max@Math Revolution » Wed Feb 13, 2019 12:32 am
=>

Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

Since questions about triangles involve three variables, E is most likely to be the answer.

Conditions 1) & 2)
If the sides given are legs, then the area of the right triangle is (1/2)*3*4 = 6.
If one leg has length 3 and the hypotenuse has length 4, then, by Pythagoras' theorem, the length of the other leg is √(4^2 - 3^2) = √7, and the area of the triangle is (1/2)*3*√7 =(3√7)/2.
Thus, both conditions together are not sufficient, since they do not yield a unique solution.

Therefore, E is the answer.
Answer: E

In cases where 3 or more additional equations are required, such as for original conditions with "3 variables", or "4 variables and 1 equation", or "5 variables and 2 equations", conditions 1) and 2) usually supply only one additional equation. Therefore, there is an 80% chance that E is the answer, a 15% chance that C is the answer, and a 5% chance that the answer is A, B or D. Since E (i.e. conditions 1) & 2) are NOT sufficient, when taken together) is most likely to be the answer, it is generally most efficient to begin by checking the sufficiency of conditions 1) and 2), when taken together. Obviously, there may be occasions on which the answer is A, B, C or D.
Join the discussion