题目信息
Khalil drove 120 kilometers in a certain amount of time. What was his average speed, in kilometers per hour, during this time?
A:Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B:Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C:BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D:EACH statement ALONE is sufficient.
E:Statements (1) and (2) TOGETHER are NOT sufficient.
参考答案及共享解析
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已选答案：
正确答案：
A:Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Algebra Applied problems
Let r be Khalil's average speed in kilometers per hour and let t be Khalil's time in hours. Then rt = 120, or t =
. What is the value of r ?
If Khalil's speed had been (r + 5) kilometers per hour, then his driving time would have been
hours.
Although there are two possible values for r, namely r = −45 and r = 40, only the positive value of r is consistent with the context. Therefore, r = 40; SUFFICIENT.
If Khalil's speed had been 1.25r kilometers per hour, then his driving time would have been 0.8t hours. It follows that (1.25r)(0.8t) = 120, or rt = 120, which provides no additional information to the given information; NOT sufficient.
The correct answer is A;statement 1 alone is sufficient.
Let r be Khalil's average speed in kilometers per hour and let t be Khalil's time in hours. Then rt = 120, or t =
. What is the value of r ?If Khalil's speed had been (r + 5) kilometers per hour, then his driving time would have been
hours.Although there are two possible values for r, namely r = −45 and r = 40, only the positive value of r is consistent with the context. Therefore, r = 40; SUFFICIENT.
If Khalil's speed had been 1.25r kilometers per hour, then his driving time would have been 0.8t hours. It follows that (1.25r)(0.8t) = 120, or rt = 120, which provides no additional information to the given information; NOT sufficient.
The correct answer is A;statement 1 alone is sufficient.
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