Our beloved mutt, Ida, came to us as a yipping puppy at our front porch after having been dumped alongside the curb 12 years go. Now, sadly, she is having trouble eating hard dog food (or maybe we are just getting soft). The question is, How much wet dog food should we buy? How much will this cost? The container gives the amount per poundage of the dog--a perfect middle school proportion problem! Allow your child to figure it out any way they like. Then show them how to write it as a proportion. Here are Ida’s numbers.
1st: Figure out how much Ida weighs.
Have your child stand on the bathroom scale and record the weight (119.2 lbs). Then have the child stand on the scale holding Ida (155.2 lbs). Subtract to get the weight of Ida. 155.2-119.2 =36 lbs.
2nd: Read the can to see how much to give per pound.
Our wet dog food is 1 oz of dog food per pound of dog, so Ida needs 36 oz.. If the can is 10 oz, Ida would need about 3.5 cans per day.
3rd: Figure the cost per day.
If 3 cans is $1.95 cents, how much would 3.5 cans be?
You could find the cost of one can--the unit price-- ($1.95/3 = .65), and then take .65*3.5 cans = $2.28.
Or you could set up a proportion, as taught in 6th-8th grades.
3 cans/$1.95 = 3.5 cans/n Solve by taking 3.5*1.953= $2.28.
As always, have fun with your child as you calculate and share possible strategies. The purpose is positive parent-child involvement with math. This will help motivate the child to learn at school.