Maths Olympiad Prep

Library / /146 of 183

, 2024

Algebra Difficulty 2.7 Junior Find the answer Canada

Five different integers in a list have a median of 1010 and a range of 77. What is the smallest possible integer
in the list?

Pick one

Solution

Consider the following list of 55 integers, ordered from smallest to
largest, and having a median of 1010:
a,b,10,c,da,b,10,c,d.

Since aa is the smallest integer in
the list and dd is the largest, and
the list has a range of 77, then
dd is 77 more than aa.

Since aa and dd differ by 77, then to find the smallest possible
value of aa, we can find the
smallest possible value of dd and
subtract 77.

The 55 integers in the list are
different from one another, and so the smallest possible value of cc is 11 (cc must be greater than the median 1010), and the smallest possible value of
dd is thus 1212.

Since dd is 77 more than aa, then the smallest possible integer in
the list is 127=512-7=5.

(We note that 5,b,10,11,125,b,10,11,12, where
bb is greater than 55 and less than 1010, is such a list.)

Want a route through all this instead of an archive? The track puts 2,444 problems in a working order, from Junior Challenge level to the IMO shortlist.

Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty) added by this project.