When do you use the guess and check method?

Question

Eva Adamson · Accepted Answer

You should use the guess and check method when you do not know how to solve a problem.

The guess and check method includes:

make a logical guess
test your guess
adjust your guess based on results of #2 until you are correct
Example:

There are 20 children in the kindergarten class. The children are a mix of 5 year olds and 6 year olds. The total age of the children equals 108 years. How many 5 year olds are there?

Guess & check method:
1. Let's guess that there are 10 five year olds.
2. If there are 10 five year olds, there must be 10 six year olds since there are 20 children in total. Their combined age is equal to (10 x 5) + (10 x 6), or 110 years.
3. Since 110 years is greater than 108 (the correct answer), our initial guess was incorrect. To get closer to the correct answer, we need to guess a higher number of five year olds (since five years is less than six years).
4. Let's now guess that there are 12 five year olds.
5. If there are 12 five year olds, there must be eight six year olds since there are 20 children in total. Their combined age is equal to (12 x 5) + (8 x 6), or 108 years. Therefore, the correct answer is 12 five year olds.

Ethan Adkins · Answer

undefined You use the guess and check method when you are trying to find a solution to a problem and you don't have a clear strategy or formula to follow. It involves making guesses or trying different options, checking each one to see if it works, and adjusting your approach based on the results. This method is often used in problem-solving situations where other methods, such as algebraic manipulation or systematic calculations, are not immediately obvious or efficient.