Q&A - P5 Math

[tianzhu]

MUMMYOF3:

Hi Tianzhu,

Thanks. My boy got the ans as 136 too but different working as yours. Not sure if the following is acceptable ?

Hi MUMMYOF3

You’re welcome.

There is usually more than one way to go about.

So long as he understands the logic behind his workings,it is acceptable.

Some students may also see it this way.

540/4 ----- 135
135 + 1 ----- 136

More importantly is students are able to apply the concepts to solve similar type of questions in examinations.

Best wishes

[Chan09]

Need some help:

Tan bought some mangoes and apples for $86.50. A mango and an apple cost $11 in all. He bought more mangoes than apples and the mangoes cost $42.50 more. How many apples did he buy?
Ans: 4

Thank you

[tianzhu]

Chan09:

Tan bought some mangoes and apples for $86.50. A mango and an apple cost $11 in all. He bought more mangoes than apples and the mangoes cost $42.50 more. How many apples did he buy?

Hi

You may use “Grouping Concept”.

86.5 – 42.5 -------44

Consider a group of 1 mango and 1 apple that costs $11

44/11 ----- 4

There are 4 groups.

Hence, 4 apples

Best wishes

[Chan09]

Couldn’t figure this one: what is the greatest number of right angles that a 5 sided figure can have? Ans: 4

I couldn’t draw the figure? Thanks

[tianzhu]

Chan09:

Couldn't figure this one: what is the greatest number of right angles that a 5 sided figure can have? Ans: 4

I couldn't draw the figure? Thanks

Hi

Just throwing up some thoughts, I am not sure if we can count the right angles formed by adjacent perpendicular lines.

Best wishes.

http://farm7.static.flickr.com/6188/6108205460_6cbc7a4bc7_z.jpg\">

[linden2000]

Hi. Just my thoughts below:


Sum of interior angles of n-sided polygon is (n-2) x 180 degrees
so sum of interior angles of 5-sided figure = (5-2) x 180 = 540 degrees

If max no. of right angles is 4, that will mean the remaining last angle is
540 - 4x90 = 180 degrees

That’s only possible if you allow for collinear vertices, ie vertices that lie in
same straight line. But that will mean a 4-sided figure is the same as a 5-sided figure.

Else if no collinear vertices allowed, would think max no. of right angles is 3.

[Chan09]

Tks as felt question was a bit misleading.

[Jcong]

Pail A contained 7/17 of the amount of water in Pail B. Pail C contained 1/9 of the total amount of water the three pails had. If Pail A and Pail B contained 5.25 litres of water more than Pail C, how much water did Pail B contain? (give the answer in litres)

[tianzhu]

Jcong:

Pail A contained 7/17 of the amount of water in Pail B. Pail C contained 1/9 of the total amount of water the three pails had. If Pail A and Pail B contained 5.25 litres of water more than Pail C, how much water did Pail B contain? (give the answer in litres)

Hi

Pail A ----- 7 units

Pail B ----- 17 units

Multiples of 9 ------- 9, 18,27 ………

1/9*27 -----3 units

Pail C ------ 3 units.

24units – 3 units ------ 21units

21units ----- 5.25

1unit ----- 0.25

Pail B -----17*0.25 ------- 4.25

Best wishes

[Jcong]

Why do you use multiple of 9? and why is 27 chosen instead of other numbers like 18? So sorry don’t really understand. Thanks