Sometimes guessing is the best strategy to use in
solving a problem.

But what do we mean by guessing?

You can guess by using information from the problem along with other ideas and strategies that you already know.

Let's look at some examples when guessing is a good strategy to use.

Libby's Girl Scout troop is making shirts for
a sewing badge. 
Each shirt had 6 buttons and there are 12 girls in the troop. 
How many buttons will
they need?

You can make a guess of how
many buttons she will need.
You know that 6 x 10 = 60.
But, since 10 is 2 less than 12,
you will need 2 more 6s.

So, you would have a good guess by adding 60 + 6 + 6.
Your guess would be 72 buttons.

Jack and Jill were collecting cans to raise money for their band trip. 
Together they collected 24 cans, but Jill collected
4 more than Jack.
How many did they each collect?

You can make a guess of how
many cans they each collected.

Let Jill = {}
Let Jack = []
{} + [] = 24
{} - [] = 4

If {} = 14 and [] = 10
You have the correct guess.
14 + 10 = 24
14 - 10 = 4

Patty bought a magazine that cost $3.20 and paid with 4
$1 bills. If she received
4 coins in change,
what coins did she receive?

First you need to subtract to
find the change.
$4.00 - $3.20 = $ .80

What 4 coins will equal $ .80 ?

Guess:  3 quarters and 1 nickel
Check the guess: $ .75 + $ .05 = $ .80