a hollow iron pipe is 21 cm long and its external diameter is 8 cm. if the thickness of the pipe is 1 cm and iron weighs 8 g / cm ^ 3, then the weight of the pipe is:
Choose the correct option
A) 3.6 kg
B) 3.696 kg
C) 36 kg
D) 36.9 kg
E) 3.06 kg
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">pi * (4 ** 2) * 21</gadget>
<output>336*pi = around 1_055.575132</output>

<gadget id="calculator">4 - 1</gadget>
<output>3</output>

<gadget id="calculator">pi * (3 ** 2) * 21</gadget>
<output>189*pi = around 593.761012</output>

<gadget id="calculator">(336*pi) - (189*pi)</gadget>
<output>147*pi = around 461.81412</output>

<gadget id="calculator">(147*pi) * 8</gadget>
<output>1176*pi = around 3_694.512961</output>

<gadget id="calculator">(1176*pi) / 1_000</gadget>
<output>147*pi/125 = around 3.694513</output>

<result>B</result>
a hollow iron pipe is 21 cm long and its external diameter is 8 cm. if the thickness of the pipe is 1 cm and iron weighs 8 g / cm ^ 3, then the weight of the pipe is:
divide(multiply(subtract(volume_cylinder(divide(8, const_2), 21), volume_cylinder(subtract(divide(8, const_2), 1), 21)), 8), const_1000)
"external radius = 4 cm , internal radius = 3 cm . volume of iron = ( 22 / 7 x [ ( 4 ) ^ 2 - ( 3 ) ^ 2 ] x 21 ) cm ^ 3 ( 22 / 7 x 7 x 1 x 21 ) cm ^ 3 462 cm ^ 3 . weight of iron = ( 462 x 8 ) gm = 3696 gm = 3.696 kg . answer b"