The box being used is 11cm by 30cm. How do I convert this to inches using proportions?

Question

6th grade math question

Answer 1

1 inch = 2.54 cm  ⇐ A basic conversion fact that you should memorize FOREVER. Therefore

1 cm = 1/2.54 in

1 cm = 0.3937"  This factor can replace the cm units, i.e. 11 cm = 11(0.3937 in) = 4.3307 in.