Hello and welcome to Problem Solving Strategy Number 5: Guess and Check.
In this video you'll learn how to solve a math problem by guessing an answer,
and then checking that it makes since in the problem.
Did you know that experienced mathematicians often use the guess and check method to solving problems?
That's because when two or more things in a problem are unknown,
we have to try and try again to get proof that our answer is the right one.
But, be careful.
Guesses should be educated guesses.
In other words, they should make since to the problem and shouldn't be wild guesses.
Be sure to read the problem closely.
Let's look at an example to understand how to guess and check.
"I am a 2-digit number.
I have a 3 in the ones place.
I am greater than 45 but less than 63.
What number am I?"
We know right away that we have to guess the number to solve this problem.
What else do we know?
We know the final answer will be a two digit number.
We also know for sure that there is a 3 in the ones place.
Where is the ones place?
You got it.
We know the number will be greater than 45, or bigger than 45.
So, would it make since to put a big cow in the tens place?
No.
Why not?
We're making a guess aren't we?
Ha. Of course!
We can make guesses in math, but they can't be wild guesses.
They have to make since to the problem.
In this case, we're looking for digits, not animals.
Good catch.
OK, so can the digit in the tens place be a 4?
No. You're right.
That would make the number less than 45, wouldn't it?
Good guessing and checking.
Let's guess another digit.
Could there be a 7 in the tens place?
No again.
That would make the number greater than 63.
Remember that the problem says that the final number is greater than 45,
but less than 63.
Can you now make an educated guess to solve this problem?
If you guessed 5 in the tens place, that makes the final answer 53.
To know if we're right, let's read the whole problem again.
"I am a 2-digit number."
Yes we have two digits.
"I have a 3 in the ones place."
Yes. We have a 3 in the ones place.
"I am greater than 45."
Yes. 53 is greater than 45.
"But, less than 63."
Yes. 53 is indeed less than 63.
We got it.
We made some educated guesses and we solved this problem.
Congratulations!
You learned another trick to solving word problems.
Sometimes you need to make smart or educated guesses,
and then check your answers to see if it makes since in the problem.
Just remember that guesses have to make since.
They can't be wild guesses.
Need more practice guessing and checking?
You can find lots of word problems in our games.
Have fun and always be clever.