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Unit review: divisibility rules
Textbook: Part 1, unit review, pp. 64–65
GoalSum up divisors, multiples and the divisibility rules.
New words
divisor · bo‘luvchimultiple · karralirule · alomatsum of digits · raqamlar yig‘indisi
Explanation
To recap: 10 – the last digit is 0; 5 – the last digit is 0 or 5; 2 – the last digit is even; 4 – the number made by the last two digits is divisible by 4; 3 and 9 – the digit sum is divisible by 3 or 9. We find the divisors of a number from pairs 1 × a, 2 × b, …
Worked examples
3 780: the last digit is 0, the digit sum is 18 and the last two digits are 80, so it is divisible by 2, 3, 4, 5, 9 and 10.
Divisors of 28: 1 × 28, 2 × 14, 4 × 7 → 1, 2, 4, 7, 14, 28.
Class activity
“Rules relay”: teams take turns at the board writing which numbers the given number divides by, using the rules.
Practice
1
Which of 2, 3, 4, 5, 9, 10 divide 3 780?
All of them
2
From 132, 225, 348, 84, 150 write those divisible by both 3 and 4.
132, 348, 84
3
Write the smallest four-digit number divisible by 9.
1 008
4
Which of 2, 3, 4, 5, 9 boxes can 432 beads be shared into equally with none left over?
2, 3, 4, 9