139
Unit review: expressions, properties and equations
Textbook: Part 4, pp. 30–31
GoalReview expressions, properties of multiplication and equations.
New words
review · takrorlashexpression · ifodaproperty · xossaequation · tenglama
Explanation
In this unit we learned the properties of multiplication (swapping, grouping, with 0 and 1), the order of operations and equations. Remember: brackets first, then multiplication and division, then addition and subtraction. In an equation we find the unknown with the opposite operation and check the root.
Worked examples
9 + 4 × (5 − 2) = 9 + 4 × 3 = 9 + 12 = 21.
x × 3 = 18: x = 18 : 3 = 6; check: 6 × 3 = 18.
Class activity
“The tablecloth”: 6 equations are written on the board. For each root found correctly, a child places a picture card (bread, apple, grapes…) on the “tablecloth”.
Practice
1
(3 × 5) × 2 = ?
30
2
9 + 4 × (5 − 2) = ?
21
3
x × 3 = 18, x = ?
6
4
One box holds 9 notebooks. How many notebooks are in 4 boxes and 5 boxes together?
81