There are four boxes, each of them
contains exactly the same numbers:
1,2,3,...,n.
Four different numbers are drawn
from the boxes and multiplicated
with each other to get a product.
What′s the sum of all products?
Σ_(a≠b≠c≠d) abcd=?
If there is no second′s hand on
a clock and the minute and hour
hand move in continuous fashion,
then exactly at what time between
02:10 and 02:15 does the position
of the two hands exactly coincide?