Answer:
The perimeter changed by 6 cm.
Step-by-step explanation:
A rectangle has a width of 5 cm and a length of 10 cm.
The perimeter is = 2(length+width)
Perimeter = 
= 
= 30 cm
When the width is increased by 3, and lets assume that the length is same .
So, length is 10 cm and width is 8 cm.
Perimeter = 
= 
= 36 cm
Change in perimeter =
cm
So, the perimeter changed by 6 cm.