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Secondary 1 | Maths
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Eleanor
Eleanor

Secondary 1 chevron_right Maths chevron_right Singapore

Please help!!!
VERY URGENT PLEASE HELP!
thanks

Date Posted: 4 years ago
Views: 177
Eric Nicholas K
Eric Nicholas K
4 years ago
Q1 is basically asking for the list of multiplications which multiply to a certain number.

(i) 4 can be written as 1 x 4 or 2 x 2 (here, 4 x 1 is treated to be the same as 1 x 4)

(ii) 8 can be written as 1 x 8 or 2 x 4.

(iii) 12 can be written as 1 x 12, 2 x 6 or 3 x 4.

(iv) 5 can be written as 1 x 5.

(v) 7 can be written as 1 x 7.

(vi) 1 can be written as 1 x 1.

For Q2, rather than listing out everything, all we need to do is to consider all the possible factors of a given number.

For Q3, the single arrangement indicates that the number of dots is either 1 or a prime number (note that 1 is NOT a prime number).

For Q4, the multiple arrangements indicate that the number of dots is a composite number (basically, numbers which are not 1 and not prime)
Eleanor
Eleanor
4 years ago
But for question 3 and 4 i need rhe explanation
and i dont really understand what you were saying about question 1
Eric Nicholas K
Eric Nicholas K
4 years ago
For question 1, you need to arrange the dots in a rectangular format.

The number of dots can be thought of as the length * breadth of the rectangle.

We need to find values of “length” and “breadth” such that they multiply to the given number of dots.

For example, 4 dots can be arranged into a length * breadth configuration of 4 * 1 or 2*2.

In the representation,

x x x x

is a configuration of 4 * 1. You can decipher how to draw a 2 * 2 configuration.

I have listed this as the products of the numbers in the previous post.

For question 3, it is a special case of questions 1 and 2 where there is only one possible combination leading to the given number of dots. So for example, 5 dots can be classified as a length * breadth configuration of 1 * 5.

x x x x x

No other combination for 5 dots is possible without leaving gaps in between. The numbers 1 and 5 are technically the only factors of 5 (since you have listed them as the only possible way to arrange the rectangles). As such, these number of dots are essentially prime numbers.

For question 4, it is a special case of questions 1 and 2 where more than one possible arrangement is available.

6 dots, for example, can be arranged as 6 * 1 or 3 * 2. And you have just listed the possible multiplications yielding 6. As such, 6 has more than two factors (1, 2, 3, 6) and these are composite numbers.
Eric Nicholas K
Eric Nicholas K
4 years ago
So the key idea here is to relate your factors or multiplications listing with the number of dots diagrams.

You will realise that 6 can be written as 1 x 6 and 2 x 3. But why not 4 x 1.5? Because we cannot have 1.5 dots! These are the possible arrangements for the rectangles, since the number of dots along a length or along a breadth must be a whole number.
Eleanor
Eleanor
4 years ago
ok thanks!

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