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Equations: a solving plan
Textbook Part 4, pp. 56–57
GoalSolve an equation step by step and check it.
New words
plan / algorithm · algoritmpart (of an operation) · komponentcheck · tekshirish
Explanation
Plan for solving an equation: 1) write the equation; 2) decide whether the whole or a part is unknown; 3) recall the rule (part = whole − part; whole = part + part); 4) calculate; 5) write what x equals; 6) check.
Worked examples
Sabina took 3 fruits and 4 were left: x − 3 = 4. The whole is unknown → x = 4 + 3 = 7. Check: 7 − 3 = 4 ✓.
6 + x = 11. A part is unknown → x = 11 − 6 = 5. Check: 6 + 5 = 11 ✓.
Class activity
Each pair takes an algorithm card and solves one equation in 6 steps, pointing to and saying each step.
Practice
1
x + 7 = 49. x = ?
42
2
x − 3 = 4. x = ?
7
3
25 − x = 13. x = ?
12
4
A chef used 10 + 10 + 20 bunches of herbs and 30 are left. How many were there?
70