The length of B'C' in the rectangle A'B'C'D' = 9 units.
<u>Step-by-step explanation</u>:
step 1 :
Draw a rectangle with vertices ABCD in clockwise direction.
where, AB and DC are width of the rectangle ABCD.
AD and BC are length of the rectangle ABCD.
step 2 :
Now,
The length of the rectangle is AD = 5 units and
The width of the rectangle is AB = 3 units.
step 3 :
Draw another rectangle with vertices A'B'C'D' extended from vertices of the previous rectangle ABCD.
step 3 :
The length of the new rectangle is A'D' which is 4 units down from AD.
∴ The length of A'D' = length of AD + 4 units = 5+4 = 9 units
step 4 :
Since B'C' is also the length of the rectangle A'B'C'D', then the measure of B'C' is 9 units.