M is a list of 12 consecutive integers and N is a list of 31 consecutive integers. The median of N is equal to the greatest integer of M. If the two lists are combined into one list of 43 integers, how many integers are repeated?
A. 0
B. 6
C. 12
D. 15
E. 31
The OA is C.
I need help with this PS question. Can any expert explain it please? Thanks.
M is a list of 12 consecutive integers and N...
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The question implies that it doesn't actually matter what these integers are - we'd get the same answer whether set M started with -5 or 456,724. When that's the case, the easiest thing to do is pick numbers.
Since N is the larger set, I chose to start it with 1, so the set is from 1-31. The median of this set would be 16, so that's also the largest term in set M. That means that M must go from 5-16.
On these problems, it often helps to visualize on a number line:
Here, we can clearly see that all of the terms in set M are also in set N. Thus, there are 12 terms in common.
Since N is the larger set, I chose to start it with 1, so the set is from 1-31. The median of this set would be 16, so that's also the largest term in set M. That means that M must go from 5-16.
On these problems, it often helps to visualize on a number line:
Here, we can clearly see that all of the terms in set M are also in set N. Thus, there are 12 terms in common.
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
EdM in Mind, Brain, and Education
Harvard Graduate School of Education