Answer:
The minimum number of rolls to buy is 9
Explanation:
step 1
Find the perimeter of the ceiling of Katie’s living room
The perimeter of a square is equal to
![P=4b](https://img.qammunity.org/2020/formulas/mathematics/high-school/g7wa6ldnhizfqgnpwa393kjltnuv5qqfec.png)
where
b is the length side of the square
we have
![b=12\ ft](https://img.qammunity.org/2020/formulas/mathematics/middle-school/yhz9ech33o8dnoe2m5qwux5nfbapkjfm05.png)
so
![P=4(12)=48\ ft](https://img.qammunity.org/2020/formulas/mathematics/high-school/y61r65nql7yzlxnrljexsa7qndakr2uiqi.png)
step 2
Find the length side of the diagonals of the ceiling
Applying Pythagoras theorem
![d=\sqrt{12^(2) +12^(2)}\\ \\d=√(288)=16.97\ ft](https://img.qammunity.org/2020/formulas/mathematics/high-school/54bzy73k9swsjzkuuexbz9hq41fir9fmts.png)
step 3
Find the total crepe paper needed
Sum the perimeter plus two times the length side of the diagonal
![48\ ft+2*(16.97\ ft)=81.94\ ft](https://img.qammunity.org/2020/formulas/mathematics/high-school/tuthof1s9hsoppbxztzy887xblb4c8s9sp.png)
step 4
Find the number of rolls needed
we know that
Each roll contain 10 ft of crepe paper
so
![81.94/10=8.19\ rolls](https://img.qammunity.org/2020/formulas/mathematics/high-school/yv852cgjtgpxzqtonru2g6vhgz5q6yfy70.png)
Round up
![8.19=9\ rolls](https://img.qammunity.org/2020/formulas/mathematics/high-school/a7ueyci4l291h0f77ji6ybh7n03e1b2dea.png)
The minimum number of rolls to buy is 9