Egypt Primary 3 Mathematics, Week 28: The six and seven facts

Strategies, sixes and sevens, and elapsed time

Week 28 · Adding, subtracting, sixes and sevens · 3 lessons

The six and seven facts

Discover Mathematics P3: Term 2, Lessons 111–120

GoalLearn the six and seven multiplication facts using doubles, break-apart and dice.

New words

multiple · a number in the counting pattern of another number, such as 42 for 6break apart · to split a fact into easier factssum · the answer to an addition

Explanation

Sixes: 6, 12, 18, 24, 30, 36, 42, 48, 54, 60. Use a fact you know. Six is 5 + 1, so 6 × 7 = 5 × 7 + 1 × 7 = 35 + 7 = 42. You can also double the threes: 6 × 8 is double 3 × 8, and 24 + 24 = 48. Sevens: 7, 14, 21, 28, 35, 42, 49, 56, 63, 70. Seven is 5 + 2, so 7 × 8 = 5 × 8 + 2 × 8 = 40 + 16 = 56. Order does not matter, so 6 × 7 and 7 × 6 are both 42. Here is a game: roll two dice, add the dots and multiply the sum by 7. If the dice show 3 and 5, the sum is 8 and 8 × 7 = 56.

Number	× 6	× 7
1	6	7
2	12	14
3	18	21
4	24	28
5	30	35
6	36	42
7	42	49
8	48	56
9	54	63
10	60	70

Worked examples

Find 6 × 7 by breaking the 6 into 5 and 1. The array has 5 rows of 7, which is 35, and 1 more row of 7. So 6 × 7 = 35 + 7 = 42.

Roll two dice. They show 3 and 5. The sum is 3 + 5 = 8. Multiply by 7: 8 × 7 = 56. Check by breaking apart: 8 × 5 = 40 and 8 × 2 = 16, and 40 + 16 = 56.

The fact triangle for 6, 7 and 42 shows that 6 × 7 = 42, 7 × 6 = 42, 42 ÷ 6 = 7 and 42 ÷ 7 = 6. Knowing one sixes fact gives us a sevens fact.

Class activity

Dice sevens. Roll two dice ten times. Each time add the dots, multiply the sum by 7 and write the equation, such as 9 × 7 = 63. Circle the facts you answered without counting on your fingers. Practise the others and play again.

Practice

Find 6 × 8 by doubling 3 × 8.

Find 7 × 7 by breaking apart 7 into 5 and 2.

The two dice show the dots in the picture. Find the sum, then multiply it by 7.

There are 7 days in a week. How many days are there in 9 weeks?

Six children each have 12 stickers. How many stickers do they have altogether?