Question #cd663

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Answer 1 · 2016-10-02T13:35:17

#115# pots can be painted completely

The first problem you should see is that there are two different units.
#m^2 and cm#

Converting units of area is more tricky than just lengths, so let's change #cm # to #m# right at the beginning. For #cm rarr m, div 100#

#"radius " = 15cm = 0.15m and "height "20cm = 0.2m#

Once we know the surface area of 1 pot, we can just divide #30m^2# by that answer to find how many of the same pots can be painted.

Each pot has a base ( a circle) and the curved part.
You should know those formulae
Circle Area =#pir^2# Curved surface area = #2pirh#

Total outside area of one pot =# pir^2 + 2pirh#

#SA=pi(0.15)^2 +2pi(0.15)(0.2)#
#SA =0.0225pi +0.06pi#
#SA = 0.0825pi" "m^2" "larr# leave it in terms of #pi# for now

How many pots can be painted? Divide 30 by the area of one pot.

#30/(0.0825pi) = 115.749#

Now be careful... Although the first decimal is more than 5, do not round up...

This means that 115 pots can be painted completely but only about #3/4# of the next pot gets done.