# Math word problem – solve 2 variables given their sum and difference

Posted in : stlplace

There are a few ways to solve for it. I am aware of 3.

1. For the problem above, I tried to guess 1st. Because the numbers are easy.
2. A few years ago I came across the bar model approach from “Math in Focus“, because the school my daughter attends start adopting that math curriculum. Below is another similar word problem and my #barModel solution for it: the total number of adults and kids are 6872, and the number of adults are 2150 more than the number of kids.

3. Use the equation approach. Kids usually started to learn equations from algebra, which in the USA is usually from grade 6, 7 or 8 (again this depends on the school and the kid’s math level).

For the 1st problem: x + y = 1.10 and x -y = 1.00

(add those two equations together) =>

x = 1.05 and y = 0.05

Bonus point: try to solve the 2nd problem using the equation approach.

Bonus problems : try any of the problems in my collection.

Also, here is one more using bar model.

One more problem, solution is shown below. We have 3 boxes

holding total of 4,000 grams of candy

We know the 1st box holds twice as much as the 2nd box, and 3rd box holds the amount of 2nd box plus 60 grams.

A: 2nd box has 985 grams. 1st box has 1,970 grams and 3rd box has 1,055 grams. Bar model is shown below.

One more interesting (hopefully not too hard 🙂 problem, curtesy of PragmaticProgrammers (https://twitter.com/pragprog)

Have fun with math as you solve the integer number for the question mark:

🐂 = 🐟 – 3
🐂 = 🦃 + 2
🐟 = 3 X 🦃 + 3
🦃 + ? = 7

(Update 10-20-2023) I worked with my 4th grader on 2 more word problems. I don’t think they are easy problems for a 4th grader. But at the other hand, I can understand why she whines about those type of problems, and while I don’t appreciate her whining. I will do my part: try to explain my thinking, and hopefully she will get better solving those.

On a separate yet related note, since I just had parent teacher conference with my 8th grader math teacher, and had conversations with my 8th grader, one thing I can say for many parents is: try to hang in there. Try to help the kid so that he/she don’t fall behind too much.