Practice GMAT Data Sufficiency Question
Return to the list of practice GMAT data sufficiency questions.
Police suspected that motorists on a stretch of I-75 often exceeded the speed limit yet avoided being caught through the use of radar detectors and jammers. Officer Johnson of the State Police recently pulled over a driver on I-75 and accused him of breaking the 50 mile-per-hour speed limit. Is Officer Johnson’s assertion correct?
- Officer Johnson noted that the driver had traveled 30 miles from point A to point B on I-75.
- Officer Johnson noted that it took the driver 30 minutes to travel from point A to point B on I-75.
Correct Answer: C
- The basic equation necessary for solving this problem is:
Distance = Rate*Time
D = RT
If Officer Johnson can prove that R, the driver’s average rate or speed, exceeded 50 miles-per-hour, Officer Johnson can prove that the driver broke the speed limit. We must be able to find R in order to definitively answer the question of whether Officer Johnson’s assertion is correct.
-
Evaluate Statement (1) alone.
- Statement (1) indicates that D = 30 miles. Without information about T or R, we cannot find the value of R and, as a result, we cannot prove or disprove Officer Johnson's claim.
- Statement (1) alone is NOT SUFFICIENT.
-
Evaluate Statement (2) alone.
- Statement (2) indicates that T = 30 minutes. Without information about D or R, we cannot find the value of R and, as a result, we cannot prove or disprove Officer Johnson's claim.
- Statement (2) alone is NOT SUFFICIENT.
-
Evaluate Statements (1) and (2) together.
- From Statement 1: D = 30 miles
- From Statement 2: T = 30 minutes
- Putting the information together, we can construct the following algebraic equation:
D = RT
30mil = R(30min)
R = 1mil/1min = one mile per minute
R = One mile per minute * 60 minutes per hour = 60 miles per hour.
- Since we have a value for R, we can definitively judge the veracity of Office Johnson's claim.
- Statements (1) and (2), when taken together, are SUFFICIENT.
- Since Statement (1) alone is NOT SUFFICIENT and Statement (2) alone is NOT SUFFICIENT, but Statements (1) and (2) when taken together are SUFFICIENT, answer C is correct.
Return to the list of practice GMAT data sufficiency questions.