Help Me To:
Eligible Content M3.D.2.1.2
Help Me To:
Choose the number sentence that matches a given story (one operation + or – only)
Did You Know?
In a math story/word problem, you add (+) to join groups of different
amounts. You subtract ( - ) to take
away or compare amounts.
Look at the examples of symbols below.
Match the highlighted words to the colored numbers and symbols in the number
sentences to identify
the parts of an equation.
Number sentences or equations contain numbers, operation
symbols (which may include a plus sign,
a minus sign, a multiplication sign, or a division sign), and an
equal sign followed by an answer.
In this lesson, we will concentrate on two operations ( + and - ).
3 + 2 = 5
5 - 2 = 3
Check What You Know First
Choose the number sentence
that matches the math problem. Then
solve the problem.
Write A or B. Then
write the
number for
the answer.
Mary had 2 cats named Gadget and Gizmo. Gizmo weighs 12 pounds and
Gadget weighs 9 pounds.
How much more does Gizmo weigh than Gadget?
A. 12 + 9 = ___
B. 12 – 9 = ___
Mary buys 9 cans of cat food. She already has 8 cans of cat
food at home. How many cans does she
have altogether?
A. 9 + 8 = ___
B. 9 – 8 = ___
Mary had to return 4 books on cats to the library. Her
friend Jill asked her to return some
books of hers, too. Altogether, Mary returned 7 books to the
library. How many of her
friend’s books did Mary return?
A. 4 + ___ = 7
B. 7 - 3 = ___
Key Vocabulary
A plus sign ( + ) is a mathematical symbol which means to add numbers.
A minus sign ( - ) is a mathematical symbol which means to subtract numbers.
An equal sign ( = ) is a mathematical symbol
used which means is equal to.
Example: 3 < 6
A number sentence is a sentence that includes numbers, operation
symbols, and a greater than or
less than symbol or an equal sign. Examples: 3 + 2 = 5, 5 – 2
= 3, 4 + 1 < 6, 8 – 2 > 5
An expression is the part of a number sentence that combines
numbers and operation signs, but doesn’t
have an equal sign or an inequality sign. Examples: 3 + 2, 5
- 2
An equation is a number sentence which states that two amounts are equal. Examples: 3 + 2 = 5, 5 – 2 = 3
An inequality is a mathematical sentence that compares two
unequal expressions with symbols < (less than)
or > (greater than). Examples: 4 + 1 < 6, 8 – 2 > 5
An inverse operation is an opposite operation, or operations
that undo each other, such as addition and
subtraction or multiplication and division. Examples: 3 + 2 = 5, 5 – 2
= 3, 4 x 3 = 12, 12 ÷ 3
= 4
A variable is a symbol or letter that stands for an unknown number. Example: a + 2 = 5, 6 + 2 = n
A fact family is a set of related multiplication and division,
or addition or subtraction, equations
using the same numbers.
Examples: 2 x 4 = 8, 4 X 2 = 8, 8 ÷ 4
= 2, 8 ÷ 2 = 4, 1 +
5 = 6, 5 + 1 = 6, 6 – 5
= 1, 6 – 1 = 5
Learn About It Now
In order to match a story to a given combination
of operation symbols ( +, -, x, ÷
), you need to
know when to choose a particular operation. Refer to the following chart to determine when you add,
subtract,
multiply and divide.
You can also look for KEY Words in math story problems. Refer to the chart below.
ADD If you read:
|
Sum |
SUBTRACT if you read:
|
Remainder |
MULTIPLY if you read:
|
Find the product |
DIVIDE if you read:
|
Quotient |
Let’s review the problems we already did by using the charts
above to help determine what the number
sentence would be.
Mary had 2 cats named Gadget and Gizmo. Gizmo weighs 12 pounds and
Gadget weighs 9 pounds.
How much more does Gizmo weight than Gadget?
In this problem, the key words are (how much more) which
indicates that one should subtract the numbers in the math word problem.
You would subtract 12 minus 9 to get a difference of 3. (The
number sentence is 12 - 9 = 3).
Mary buys 9 cans of cat food. She already has 8 cans of cat
food at home. How many cans does she
have altogether?
A. 9 + 8 = ___
B. 9 – 8 = ___
In this problem, the key word is (all together) which indicates
that one should add the numbers in the math word problem.
You would add 9 plus 8 to get a total of 17. (The
number sentence is 9 + 8 = 17).
Mary had to return 4 books on cats to the library. Her friend
Jill asked her to return some books of hers, too.
Altogether, Mary
returned 7 books to the library. How many of her friend’s books
did Mary return?
In this problem, you will use the addition equation to solve the problem. (The
number sentence is 4 + __ = 7).
Mary has 4 books. To obtain the total of 7, you need to add 3 more to
4. Mary returned 3 of her friend’s books.
Using Variables in an Equation to Match a Story/Word Problem
When you do not know what number to use in a number sentence,
you can use a symbol or letter to represent the
unknown number. This
symbol or letter that stand for an unknown number is called a variable. Look
at the following problem.
Susan has 9 cookies on a tray. She put some more cookies on the tray.
We do not know how many more cookies she put on the tray so we can use a variable to
represent the unknown quantity.
The expression would be:
9 + m
or
9 cookies plus some more cookies
An expression is the part of a number sentence that combines
numbers and operation signs, but doesn’t have an equal sign
or an inequality
sign. The letter m in the expression is called a variable. It stands
for the number we do not know.
We can add to this same problem to make an equation.
Susan has 9 cookies on a tray. She put some more cookies on
the tray. Now she has 16 cookies in all.
How many cookies did
she add to the tray?
Now we have an equation. An equation is a number sentence stating that two amounts are equal.
9 + m = 16
or
9 muffins plus some more muffins equals 16 muffins.
If we have 9 muffins already and add 7 more, we will get a total of 16 muffins.
More Practice With Story/Word Problems
Choose the number sentence that matches the math problem. Then
solve the problem.
Write A,
B, C or D. Then
write the number for the answer.
Sam had 5 pencils. He obtained some extra pencils. Now he has 20 pencils. How many additional pencils did he get?
A. 20 - p = 5
B. p + 6 = 20
C. 5 + p = 20
D. 20 - 15 = p
Sam had 10 pieces of candy. He gave some away. Now he
has 3 pieces of candy. How many pieces did
he give away?
A. 10 - 5 = c
B. 10 - c = 3
C. 10 + 3 = p
D. 10 x 3 = p
Websites to Check Out For Extra Practice
Click below for some fun games to practice solving math word problems and choosing the correct operation.
http://www.harcourtschool.com/activity/operation_snowman/
http://www.harcourtschool.com/activity/operation_blustery_day/
http://www.harcourtschool.com/activity/operation_thunderstorm/
http://www.harcourtschool.com/activity/operation_power/
http://www.harcourtschool.com/activity/operation_domino/
http://www.harcourtschool.com/activity/escape_planet_x/
Click below to practice solving equations.
http://www.aaaknow.com/equ725x2.htm Equations 1
http://www.aaaknow.com/equ725x3.htm Equations 2
http://www.aaaknow.com/equ18cx2.htm Addition Equations with 1 digit numbers
http://www.aaaknow.com/equ27fx2.htm Addition Equations with 2 digit numbers
http://www.aaaknow.com/equ18dx2.htm Subtraction Equations with 1 digit numbers
http://www.aaaknow.com/equ28fx2.htm Subtraction Equations with 1 digit numbers
Click below to sharpen your math-problem-solving skills
This
website was designed by two fourth graders for fourth graders to practice word
problems.
http://library.thinkquest.org/4471/
Enjoy
more than 600 interactive word problems for grades K – 3 at this website.
http://www.mathplayground.com/wpindex.html
Grand
Slam Math is an interactive program designed to help you become better at solving
word problems.
Level 1 contains 15 addition and subtraction word problems. Level 2 contains
12 multiplication and division
word problems.
http://www.mathplayground.com/GSMbegin.html
Hoops
provides word problem practice for students in grades 3 to 5. All word problems
use whole numbers only
but the problems range from single step addition to multistep equations. There
are also problems that require
students to interpret remainders.
http://www.mathplayground.com/MathHoops_Z1.html
Good
explanation solving word problems and setting up equations.
http://www.homeschoolmath.net/teaching/teach-solve-word-problems.php
