25
Subtracting (43 − 7)
Textbook: Part 1, lesson 24, pp. 52–53
GoalPractise the 43 − 7 method; two-step expressions and equations.
New words
minuend · kamayuvchisubtrahend · ayriluvchidifference · ayirmaorder of operations · amallar tartibi
Explanation
In an expression without brackets we work from left to right: 45 − 9 + 4 = 36 + 4 = 40. In a table, minuend − subtrahend = difference. If one is unknown we get an equation: 42 − y = 7, so y = 42 − 7 = 35.
Worked examples
72 − 6 + 4 = 66 + 4 = 70.
f + 6 = 25 → f = 25 − 6 = 19.
Class activity
“Chain”: each child continues from the previous answer: 45 − 9, then the answer − 6, and so on. If the chain ends without a mistake, everyone wins.
Practice
1
45 − 9 + 4 = ?
40
2
56 − 8 + 2 = ?
50
3
42 − y = 7. y = ?
35
4
A shop had 65 cubes. 3 were sold in the morning and 3 more later. How many are left?
59