Question

Dona paints ornaments for a school play. Each ornament is as shown and is made up of two identical cones. She uses one bottle of paint to paint 202 cm2. How many bottles of paint does she need in order to paint 70 ornaments? Use 3.14 for pi.1. The surface area of one ornament is about ___cm2.2. She needs ___ bottles.

Answer 1

The surface area of a cone is given by the following formula:

`SA=\pi rs+\pi r^2`

Where SA is the surface area, s is the slant and r is the radius. Replace for the given values:

`\begin{gathered} SA=(3.14)\cdot(2.7)\cdot(8.6)+(3.14)\cdot(2.7)^2 \\ SA=72.91+22.89 \\ SA=95.8 \end{gathered}`

Each ornament has 2 cones, it means that each ornament has a surface area of:

`SA=2\cdot95.8=191.6`

If she needs to paint 70 ornaments, she will have to paint:

`SA=191.6\cdot70=13412`

According to the question statement, she uses one bottle of paint to paint 202cm^2. To find how many bottles she needs to paint 70 ornaments, divide the total area of the 70 ornaments by 202:

`(13412)/(202)=66.39`

The answers are:

1. The surface area of one ornament is about 191.6 cm^2.

2. She needs 67 bottles.