Question 711610
Solution:

Let 'a' be the side of the square .
When 3 squares are joined together to form a rectangle, they have to be arranged in such a way that one of the sides of the square is in contact with a side of another.

Therefore, perimeter of rectangle = top + bottom + 3 * 1 side of sq + 3*1 side of sq

Perimeter = a + a + 3a + 3a = 8a = 48 
or a = 6 in