Number (add/sub)

Hong Kong

Stage 1

Lesson

Here we will use patterns in addition to help us add two-digit and single-digit numbers. When adding ten to one addend (number), we can see a pattern in the answer.

$6+2=8$6+2=8

$16+2=18$16+2=18

$26+2=28$26+2=28

$36+2=38$36+2=38

Do you notice how the digit in the ones column stays the same and the tens digit increases by one ten each time? Let's use that knowledge to learn more about patterns in addition.

Key vocabulary

Addend: a number which is added to another number.

Commutative law: numbers can be added in any order, e.g. $5+3$5+3 is the same as $3+5$3+5.

Total: the answer when two or more numbers are added together.

Sum: the answer when two or more numbers are added together.

Number sentence: a way of writing a mathematical fact using numbers and operators (e.g. +, -, x or ÷)

$17+2=19$17+2=19

Use this to find:

$27+2=\editable{}$27+2=

$37+2=\editable{}$37+2=

$47+2=\editable{}$47+2=

$67+2=\editable{}$67+2=

$5+13=18$5+13=18

Use this to find:

$5+\editable{}=28$5+=28

$5+\editable{}=38$5+=38

$5+\editable{}=48$5+=48

$5+\editable{}=88$5+=88

What is the pattern? Choose the correct answer:

A two digit number plus $5$5 always has the same answer.

AWhen we add $5$5 to a two-digit number that ends in $3$3, we get a two-digit number that ends in $8$8.

BThe tens digit never changes when we add $5$5 to any number.

CThere is no pattern.

D

Choose the right answer.

$3+32$3+32 will be in the:

$40$40s

A$30$30s

B