WALT: Express missing number problems algebraically

Starter Think of pairs of numbers with a product of 48 Write equalities to show equivalence, e.g. 12 × 4 = 6 × 8. Repeat for divisions with answers of 4, e.g. 12 ÷ 3 = 40 ÷ 10.

25 + a = 30 This is an equation. ‘a’ stands for a mystery number. What is a?

25 + a = 30 30 25 a

6b = 42 6b stands for 6 x b What is b?

If 6 times something is 42, then the something must be 7. 6b stands for 6 x b What is b? If 6 times something is 42, then the something must be 7. 42 b b b b b b

35 ÷ c = 7

35 ÷ c = 7 C = 5

3 × 5 = 17 – d Discuss with your partner how you might work this one out.

3 × 5 = 17 – d Discuss with your partner how you might work this one out. 15 equals 17 minus something, so the something must be 2. 15 = 17 – d

3e + 1 = 18 – 5

Now... work in pairs to write their own missing number problem for another pair to solve.

Plenary What are the values of a, b and c? X 3 b a 21 56 c 12 32