Primary 1 Mathematics revision reference

Use these reminders when you want to check a fact or a word. Follow a lesson link to see the pictures and try the idea again.

Count and write numbers

Count each object once. The last number you say tells you how many.

• One ten is 10 ones.
• 34 is 3 tens and 4 ones. We say thirty-four.
• 40 has 4 tens and no ones. The zero keeps the ones place.
• First, second, third can be written 1st, 2nd, 3rd. Check which end to start from.

Read more: Numbers and relationships.

Signs and number sentences

• + means add. 3 + 2 = 5 joins 3 and 2 to make 5.
• − means subtract. 5-2 = 3 takes 2 away from 5.
• = means both sides have the same value. 5 = 3 + 2 is true too.
• × means multiply. 3 × 2 = 6 can describe 3 equal groups of 2.

Addition and subtraction are related: 3 + 2 = 5, 5-3 = 2 and 5-2 = 3. To share 6 counters equally between 2 people, give each person 3.

Work with numbers up to 100 for addition and subtraction. Multiplication stays within 40 and division within 20 in this course.

Money, length and time

• 100 cents = 1 dollar. Count cents together or whole dollars together.
• cm means centimetres. Start a ruler reading at the zero mark, not the end of the ruler.
• h means hours; min means minutes. 1 hour = 60 minutes. Half an hour = 30 minutes.
• On a clock, each step from one numbered mark to the next is 5 minutes. Use the shorter hour hand as well as the minute hand.
• am is before noon; pm is from noon until before midnight.

Read more: Measurement and shapes.

Shapes and picture graphs

• A triangle has 3 straight sides.
• A rectangle has 4 straight sides and 4 square corners. A square is a rectangle with all 4 sides equal.
• A circle has a curved boundary and no corners. A half circle is half a circle; a quarter circle is one of 4 equal parts of a circle.
• In a picture graph, check what each picture stands for. Count the pictures in the row you need.

Read more: Picture graphs.