Lower Secondary Mathematics

PSLE marks the graduation of Primary school students and their entry into Secondary schools as teenagers. Discuss all issues about Secondary schooling here.
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iwork
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Re: Lower Secondary Mathematics

Post by iwork » Sat Jan 10, 2015 11:15 pm

marstolive wrote:can anyone show me the solution for this question? C:
The HCF and LCM of two numbers, 12 and 5040 respectively. If one of the numbers is 144, find the other number.
Thanks :)
HCF = 12 = 2^2 x 3
LCM = 5040 = 2^4 x 3^2 x 5 x 7

One of the number = 144 = 2^4 x 3^2

So, the other number must have 2^2 x 3 x 5 x 7 = 420

iwork
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Re: Lower Secondary Mathematics

Post by iwork » Sat Jan 10, 2015 11:15 pm

adribaby wrote:Can anyone help pls?
What is your question?

adribaby
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Re: Lower Secondary Mathematics

Post by adribaby » Sun Jan 11, 2015 11:29 am

Hi iWork

refer to my edited post

iwork
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Re: Lower Secondary Mathematics

Post by iwork » Sun Jan 11, 2015 2:11 pm

adribaby wrote:Can anyone help?

Two race cars, car X and car Y are at the starting point of a 2-km track at the same time. Car X and car Y make one lap every 60s and every 80s respectively.
How long in seconds will it take for both cars to be back at the starting point at the same time?
Just find the LCM of 60 and 80, and that is the answer.

marstolive
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Re: Lower Secondary Mathematics

Post by marstolive » Sun Jan 11, 2015 9:09 pm

iwork wrote:
marstolive wrote:can anyone show me the solution for this question? C:
The HCF and LCM of two numbers, 12 and 5040 respectively. If one of the numbers is 144, find the other number.
Thanks :)
HCF = 12 = 2^2 x 3
LCM = 5040 = 2^4 x 3^2 x 5 x 7

One of the number = 144 = 2^4 x 3^2

So, the other number must have 2^2 x 3 x 5 x 7 = 420
:thankyou:


marstolive
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Re: Lower Secondary Mathematics

Post by marstolive » Tue Jan 13, 2015 8:05 pm

can someone help me with this?
Find the square root of 6x15x22x35x77 without using a calculator.
Thanks

Aberc
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Re: Lower Secondary Mathematics

Post by Aberc » Tue Jan 13, 2015 8:14 pm

marstolive wrote:can someone help me with this?
Find the square root of 6x15x22x35x77 without using a calculator.
Thanks
You need to express the numbers in terms of their factors, 3 x 2 x 5 x 3....., then group the common factors together, 2 squared x 3 squared x 5 squared x......, the square root of the squared factors will give you 2 x 3 x 5 x..... = ans.

Pepsi
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Re: Lower Secondary Mathematics

Post by Pepsi » Thu Jan 15, 2015 8:51 pm

Need HELP!!

Given that 360 = 2Cube x 3square x 5
a) the smallest integer, j, such that 360 x j is a perfect square
b) the smallest integer, k, such that 360 x k is a perfect cube
Find the j & k

iwork
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Re: Lower Secondary Mathematics

Post by iwork » Thu Jan 15, 2015 9:30 pm

Pepsi wrote:Need HELP!!

Given that 360 = 2Cube x 3square x 5
a) the smallest integer, j, such that 360 x j is a perfect square
b) the smallest integer, k, such that 360 x k is a perfect cube
Find the j & k
To get a perfect square, all the power must be even number.
To get a perfect cube, all the power must be multiple of 3.

So
a) j=2 x 5
b)k=3 x 5square

Pepsi
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Re: Lower Secondary Mathematics

Post by Pepsi » Thu Jan 15, 2015 9:57 pm

:thankyou:
iwork wrote:
Pepsi wrote:Need HELP!!

Given that 360 = 2Cube x 3square x 5
a) the smallest integer, j, such that 360 x j is a perfect square
b) the smallest integer, k, such that 360 x k is a perfect cube
Find the j & k
To get a perfect square, all the power must be even number.
To get a perfect cube, all the power must be multiple of 3.

So
a) j=2 x 5
b)k=3 x 5square

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