Answer:
12 cm
Step-by-step explanation:
This is a proportionality/similarity problem.
10 cm turned to 4 cm. So by how much has it decreased? In other words, <em>10 multiplied by </em><em>WHAT</em><em> is 4?</em>
0.4 is also known as the scale factor from the large diagram to the small diagram.
So how much would 30 cm become?<em> It would be 30 multiplied by the scale factor, which is </em><em>0.4</em><em>.</em>
<u>Hence, the length of the reduced diagram would be </u><u>12 cm</u><u>.</u>