Double Century

A "double century" in cricket means 200 runs! In maths, it is a fun way to explore multiplication as repeated addition, and to build multiplication tables up to 10. This chapter also introduces the idea of doubling numbers.

Multiplication — Repeated Addition
Multiplication is a quick way to add the same number many times.
3 + 3 + 3 + 3 = 12 is the same as 4 × 3 = 12.
We say "4 times 3 equals 12."

• Key Vocabulary
• Multiplicand: the number being multiplied (e.g., 3 in 4 × 3)
• Multiplier: the number of times we multiply (e.g., 4 in 4 × 3)
• Product: the answer (e.g., 12)

Doubling
Doubling a number means multiplying it by 2.
Double 7 = 7 × 2 = 14. Double 25 = 25 × 2 = 50.

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Example 1: Multiplication as repeated addition
A packet has 6 biscuits. There are 5 packets. How many biscuits?
6 + 6 + 6 + 6 + 6 = 30 OR 5 × 6 = 30 biscuits

Example 2: Using a multiplication table
Find 7 × 8.
From the table: 7 × 8 = 56

Example 3: Doubling
Double 45 = 45 × 2
= (40 × 2) + (5 × 2)
= 80 + 10 = 90

Example 4: Word problem
There are 9 rows of chairs. Each row has 6 chairs. How many chairs altogether?
9 × 6 = 54 chairs

Example 5: Missing factor
5 × ___ = 40
Think: 5 times what equals 40? 5 × 8 = 40. Answer: 8

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• Key Facts
• Any number multiplied by 0 = 0 (e.g., 7 × 0 = 0)
• Any number multiplied by 1 = that number (e.g., 7 × 1 = 7)
• Order does not change the product: 4 × 3 = 3 × 4 = 12 (this is called the commutative property)