Problem:
Let a,b,c,d,e,f,g,h,i be distinct integers from 1 to 9 . The minimum possible positive value of
gβ
hβ
iaβ
bβ
cβdβ
eβ
fβ
can be written as nmβ, where m and n are relatively prime positive integers. Find m+n.
Solution:
To minimize the value of the expression gβ
hβ
iaβ
bβ
cβdβ
eβ
fβ, we first aim to make the numerator as small as possible. The smallest positive value it can take is 1, so we try to find integers such that aβ
bβ
cβdβ
eβ
f=1.
Trying small combinations, we find that aβ
bβ
c=36=2β
3β
6 and dβ
eβ
f=35=1β
5β
7 satisfy the condition. These six integers are distinct and between 1 and 9, so they are valid.
This leaves us with the remaining three digits: 4, 8, and 9, which we assign to g, h, and i. Then gβ
hβ
i=4β
8β
9=288.
Thus, the value becomes 28836β35β=2881β.
If instead the numerator were greater than 1, say 2 or more, then the smallest possible value of the expression would be at least 5042β>2881β.
Hence, the minimum possible positive value is 2881β, and the answer is 1+288=289β.
The problems on this page are the property of the MAA's American Mathematics Competitions