If Joyce took 30 minutes to drive from Town A to Town B, what
was her average speed?
- The distance from Town A to Town B is 28 miles.
- Joyce drove at maximum speed of 65 miles per hour and a
minimum speed of 45 miles per hour in this interval.
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Statement (1) BY ITSELF is sufficient,
but statement (2) by itself is not sufficient. |
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Statement (2) BY ITSELF is sufficient,
but statement (1) by itself is not sufficient. |
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Both statements TAKEN TOGETHER
are sufficient, but NEITHER statement BY ITSELF is sufficient. |
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EACH statement BY ITSELF is sufficient. |
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The two statements TAKEN TOGETHER are NOT
sufficient.
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Countinue
Statement (2) is insufficient. The statement only gives you her fastest
and slowest speeds. Don't be caught in the trap of thinking that her average
must be the simple average of the maximum and minimum! The statement does
not tell you how long she traveled at each speed, and you'd have to know
that to find her average speed.
(If that is confusing, think about what would happen if she traveled
almost all the way, say 29 minutes, at 65 mph, and slowed to 45 mph for
only 1 minute. That would make her average speed just under 65, right?
But if it was reversed, and she traveled 29 minutes, most of the way,
at only 45, then her average speed is going to be close to 45. Make sense?
You cannot find an average from just knowing the maximum and minimum.)
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