This page
will provide practice solving problems using compatible numbers and
estimating. Click on the link below for practice using the other
two mental math strategies.
Compatible numbers are pairs of
numbers that can be computed easily. Put compatible numbers
together first, then finish the problem. Ready to try some?
Let's start with simple questions.
25 + 177 + 75
What are the
compatible numbers in this problem?
So the first
step would be what?
And the answer
is?
Solve the
following problems, using compatible numbers.
Problem
compatible
numbers
Answer
98 + 55 + 102 =
25 x 99 x 4 =
20 x 16 x 5 =
Estimation is used to either get
an approximate answer, or to see if an exact answer is reasonable.
Ready to try some? Let's start with simple questions.
Problem
rewrite
problem
Solve
7.99 x 5
x 5
20.25 ÷
4
÷
4
403 +
198 + 404
Ready to try some more
difficult problems? Check your answer, and if you need an
explanation, click on the Need Help button!
Problem
Answer
There
are 17 rows planted. Each row contains approximately 27
plants. About how many plants are needed?
If you
want to double the sugar in a recipe that calls for 3⅜cups and
you have 7 cups, do you have enough sugar?
