Percentage change in a product (area, total collection) when both factors change

This type of question, asked 4 times: CDS 1 2017, CDS 1 2019, CDS 2 2019, CDS 2 2020. All 4 questions below, oldest first.

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Question 1
CDS 1 2017
77 $If each of the dimensions of a rectangle is increased by 200%, the area is increased by$
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Question 2
CDS 1 2019
50 $The length and breadth of a rectangle are increased by 20% and 10% respectively. What is the percentage increase in the area of the rectangle ?$
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Question 3
CDS 2 2019
10 $In a hostel the rent per room is increased by 20%. If number of rooms in the hostel is also increased by 20% and the hostel is always full, then what is the percentage change in the total collection at the cash counter ?$
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Question 4
CDS 2 2020
72 $The length of a rectangle is increased by 10% and breadth is decreased by 10%. Then the area of the new rectangle is$
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Question 1