Tuesday, May 16, 2017

Dividing Fractions in Real Life

Fraction, Symbol, Icon While writing yesterday's entry, I realized I could not name any believable situations when a person would need to divide fractions.

I started with Dr Math and his examples included one my students would roll their eyes on.  It was about having 3/4 of a pizza left and wanting to know if four people could share it so each person got 2/5th of a pizza.

There is always someone in the class who would say, yes they could all share but not necessarily what they want since its in fourths, not fifths.  Another might say, who cares, they'll eat what they eat.

Another example which is more realistic states you have so much land.  You want to subdivide the land into smaller plots but the county requires that the septic system needs x amount of land.  How many plots can you sell.  This is better but its hard for my students because the houses either use a suction system or a honey bucket ( a bucket for collecting human waste)  They have no idea what a septic system is.

Another site provided some great real life examples such as you buy 7.5 yards of material to make up several pot holders.  Each pot holder requires 3/4 foot, how many pot holders can you make.  Or so many feet of rope that must be divided into lengths of 1/2 foot, how many strands will you have. Or the same using ribbon.  These are actually one's I've done myself when making things for the house.

Dividing fractions occurs in cooking when you want reduce a recipe.  I have tons of recipes which make enough for 6 and there is only me.  This means I either eat or freeze the rest of the meal or I cut the recipe so it makes enough for 2 or 3 people.  My students have such large families, they don't usually try to reduce a recipe.  Cooking around here is just throw stuff in till you have the right amount of food. 

The reality is we can come up with real life situations for dividing fractions but most of those situations are not ones people will do such as figuring out exactly how much detergent is used in each load if you have 50 oz of detergent.  I just scoop and dump.  I don't sit there and calculate the number of ounces used each time.  Besides, most instructions require you to use more than is actually needed.

A few years ago, I taught a remedial math class where I had students draw pictures visualizing dividing fractions.  I am the first to admit that it was hard because I'd never done it.  Fortunately, I had a book which showed a few problems so I could figure it out but it was not easy.

I'd love to hear some real examples which are used by people so I can share them with my students.
Thanks for reading, have a good day.