Friday, November 18, 2016

Calculating volume

Railway Fuel Tanks, Hospet, India  The other day in class, during warm-ups, we discussed the words much vs many.  Since I work with ELL students, they are always mixing the two words up.

I explained that much is usually used with quantities that cannot be counted while many indicated countable quantities.

During the conversation, the topic of calculating the amount of fuel remaining in a tank came up.  This is something that has to be calculated when you buy or sell a house.  A nice real world application.

This skill is also great to know if you want to know how many gallons your fuel tank takes.  Up here in Alaska, most people heat with fuel oil so we buy several gallons at once and its stored in cylinders connected to the house.  In addition, there are water tanks which are cylindrical although I know someone who bought a rectangular shaped one for collected rain water.

So how does one calculate the volume of a tank sitting in your yard? If its cylindrical you measure the radius of the tank and the height(length)  Next you square the radius, multiply the result by the height or length. The final step is to multiply the result by 3.1415 to get the cubic volume but you still have to divide this figure by 231 to find the number of gallons.

To find the amount used, you could use a stick, dip it and based on the depth you could easily do an approximation of the volume left.  For instance if the diameter is 30 inches and the stick is covered up to 12 inches, then 12/30 or 2/5 is left so you can multiply 2/5 by the volume such as 200 gallons so you'd have 80 gallons left.

This could be extended to certain types of travel cups, cylindrical water troughs, columns to calculate the amount of cement needed, etc. 

On the other hand if you tank is rectangular, volume is simply length times width times height.  So to find the number of gallons by dividing by 231.  This would be great for calculating the amount of water for a pool, aquariums, holding tanks, etc.

So many real world applications and possibilities for students to work through.  Where are some places students might need to know this?  Let me know what you think.