DAY 10

Comment

One approach is to split the counters into two equal rectangles. These can be fitted together again to make a new rectangle.

Answer

13 by 24, or 2 by 221, or 1 by 442.

Readers' methods

Stephen W, Peacehave BN10:
I Timesed 26 by 27 and got 442 so if you were to times that by 1 you would still have a rectangle so that is exactly what I did and that is my answer.