Percentage change in area when linear dimensions change

This type of question, asked 2 times: CDS 1 2017, CDS 2 2019. All 2 questions below, oldest first.

Try each one first, then open its answer.

Question 1
CDS 1 2017
88 $The radius of a circle is increased so that its circumference increases by 15%. The area of the circle will increase by$
Tap an option to check your answer.
Question 2
CDS 2 2019
72 $What is the percentage decrease in the area of a triangle if its each side is halved ?$
Tap an option to check your answer.