19
Review: operations within 100, equations, perimeter
Textbook: Part 1, pp. 40–41
GoalReview adding, subtracting, equations and perimeter within 100.
New words
root (solution) · ildiz (yechim)perimeter · perimetreven number · juft sonodd number · toq son
Explanation
In this lesson we review what we learned: adding and subtracting round numbers, solving equations and finding the perimeter. In an equation we first calculate the known numbers. A number ending in 2, 4, 6, 8, 0 is even; one ending in 1, 3, 5, 7, 9 is odd.
Worked examples
(5 + 5 + 1 + 1) + x = 60 → 12 + x = 60 → x = 48.
A triangle with sides 2, 3 and 4 cm has perimeter 9 cm, an odd number.
Class activity
“Even or odd”: the teacher says a sum, children work out the answer and sit down if it is even or stand up if it is odd.
Practice
1
42 + 18 = ?
60
2
80 − 61 = ?
19
3
(5 + 5 + 1 + 1) + x = 60. x = ?
48
4
Perimeter of a square with side 5 cm (in cm)?
20