Answer is D :)
hope it helps
<u>the question is </u> Calculate the value of the copper in the coin
Step 1
Find the volume of the coin
we know that
the volume of a cylinder is equal to

where
r is the radius of the coin
h is the thickness of the coin
in this problem we have
Diameter=19 mm=1.9 cm
r=D/2------> r=1.9/2=0.95 cm
h=1.5 mm=0.15 cm
substitute the values in the formula

Step 2
<u>Find the mass of copper in the coin</u>
we know that
the density is equal to

Solve for the mass

we have

substitute in the formula

Step 3
<u>Find the cost</u>
we know that
the market price of the copper is $2.15 per pound
1 pound=453.592 grams
convert gram to pounds
3.785 gr=3.785/453.592=0.0083 pounds
0.0083*$2.15=$0.018=$0.02
therefore
<u>the answer is</u>
$0.02
First we must find the volume of the cube. This is equal to side^3. 4^3=64 cubic inches. Since the pebbles are .5 pounds per cubic inch and we assume it is packed we multiply the volume by .5
This will give 32 pounds
She should use the conversion factor of 100 centimeters to 1 meter and also the conversion factor of 60 minutes to 1 hour.