Q&A - PSLE Math

[MathIzzzFun]

bobsg01:

Thanks MathIzzzFun.


:goodpost:

Hi bobsg01,

you are welcome :lol:

cheers.

[Neat]

tianzhu:

Neat:

What made you decide to multiply by 4 to get the equivalent ratio?

Hi

We are given that the total number of ducks and cows is between 20 and 40.

We are also given the ratio of the total number of ducks' legs to the total number of cows' legs is 5:9.

Given this ratio, a student is expected to find out the number of animals.

A cow has 4 legs and a duck has 2 legs.

Hence, the number showing the number of cow’s legs has to be a multiple of 4.Likewise the number showing the number of duck’s legs has to be a multiple of 2.

That’s why we multiply the given ratios 5:9 by 4 to get 20:36.

This gives us 10:9 as the ratio for the number of ducks to the number of cows. This is not within the range of 20 and 40.

Multiply by 2 to get an equivalent ratio of 20:18 which is 38 and within the range.

Best wishes

[quote]Thanks tianzhu for your detailed and clear explanation.

Thanks again.
:salute: [/quote]

[tianzhu]

Neat:

Thanks tianzhu for your detailed and clear explanation.

Hi

You're welcome.

Best wishes

[bobsg01]

Thanks in advance for your answer: :? :?


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[starlight1968sg]

bobsg01:

Thanks in advance for your answer: :? :?


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Find area or perimeter ???

[bobsg01]

Sorry for the confusion.


This is the question on top:

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[ChiefKiasu]

bobsg01:

Thanks in advance for your answer: :? :?


http://i56.tinypic.com/yktg0.jpg\">

Diameter of external circle = 14 + 14 = 28cm
Area of external circle = 14^2 * PI = 616cm^2
Diameter of external circle = 28 * PI = 88cm
Area of shaded area
= Area of external circle - Area of square - Area of 2 small circles
= 616 - 14*14 - 2 (7^2 * PI)
= 616 - 196 - 308
= 112cm^2

[ChiefKiasu]

bobsg01:

Sorry for the confusion.


This is the question on top:

http://i55.tinypic.com/2a7h2dy.jpg\">

Area of external square = 18*18 = 324cm^2
Area of circle = 9^2 * PI = 254.57cm^2
Area of shaded area = Area of external square - Area of circle
= 324 - 254.57
= 69.43cm^2

[bobsg01]

Thank you ChiefKiasu.

[bobsg01]

Area of circle = 9^2 * PI = 254.57cm^2


Sorry, what the meaning of PI ?