67
Subtracting two-digit numbers by place value
Textbook Part 2, pp. 54–55
GoalSubtract using tens-and-ones notation; apply it in problems.
New words
place units (tens, ones) · xona birliklarinumeral system · nomerlashrestorer · restavrator
Explanation
Write each place separately: 6 tens 5 ones − 5 tens 3 ones = 1 ten 2 ones = 12. Different peoples wrote numbers in different ways (Mayan, Chinese signs). Our way is handy — you can see the next number at once.
Worked examples
97 decorative bricks are needed to restore a minaret and 46 have arrived: 97 − 46 = 51 still needed.
A dinosaur park has 48 animals; 24 are plant-eaters: 48 − 24 = 24 meat-eaters.
Class activity
A “tens | ones” table on the board. Two teams take turns solving a subtraction by place and writing the answer as a normal number.
Practice
1
9 tens 5 ones − 5 tens 4 ones = ?
41
2
8 tens 7 ones − 2 tens 5 ones = ?
62
3
64 − 31 = ?
33
4
Put the sign: 78 − 35 ... 40
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