Page 25 - 新思维数学学生用书7 样章

1 Integers

Continued

c 3 × 5 = 15
Look at this statement: A number is divisible by 15 when it is divisible by

3 and by 5.
Do you think the statement is correct? Give evidence to justify your answer.

Summary checklist

I can use a test to see if a number is divisible by 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11.

1.6 Square roots and cube roots

In this section you will … Key words

• find out how square numbers and cube numbers are consecutive
related to square roots and cube roots. cube number

cube root
1 × 1 = 1 2 × 2 = 4 3 × 3 = 9 4 × 4 = 16 5 × 5 = 25
The square numbers are 1, 4, 9, 16, 25, … equivalent
You use an index of 2 to show square numbers. index

1 = 1 2 = 4 3 = 9 4 = 16 5 = 25 square number
2
2
2
2
2
You read 1² as ‘1 squared’ and you read 2 as ‘2 squared’. square root
2
4 = 16 is equivalent to 4 = 16, which is read as ‘4 is the square root of 16’.
2
The symbol for square root is .
Worked example 1.10
Work out 100 − 81.

Answer

10 = 10 × 10 = 100 and 9 = 81.
2
2
So 100 = 10 and 81 = 9.
100 − 81 = 10 − 9 = 1

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