Q&A - PSLE Math

[avell]

jieheng:

avell:

Dear all


Pls help me for the following questions:-

Qn (2)
The ratio of boys and girls on a school bus was 2 : 3. When 16 girls alighted from the bus, the ratio of the remaining boys to girls became 6:5. Find the number of children who remained on the bus.

Old Ratio
B [ ][ ] 2u

G [ ][ ][ ] 3u

New Ratio
B [ ][ ][ ][ ][ ][ ] 6u

G [ ][ ][ ][ ][ ] 5u

Since the number of the boys remained the same throughout the journey ,
modify the old ratio of the boys from 2 units to 6 units

Modified old ratio
B [ ][ ][ ][ ][ ][ ] 6u

G [ ][ ][ ][ ][ ][ ][ ][ ][ ] 9u

Compare the units of the girls of modified old ratio and new ratio ,

4 units = 16
1 unit = 4

Number of children remained on the bus = 11 units (6 units of boys and 5 units of girls) = 11 * 4 = 44 (Ans)

Hi Jieheng
Many thanks. I really appreciate it.

[jieheng]

avell:

Hi Jieheng
Many thanks. I really appreciate it.

Hi avell ,

You are welcome.

[peggy]

avell:

Dear all


Pls help me for the following questions:-

Qn (1)
4/5 of John's money is equal to 3/8 of Sarah's money. Express Sarah's money as a ratio of John's money in it simplest form (draw a model to help you to solve the sum.

Qn (2)
The ratio of boys and girls on a school bus was 2 : 3. When 16 girls alighted from the bus, the ratio of the remaining boys to girls became 6:5. Find the number of children who remained on the bus.

Hi,

Any MD please? I'm quite lost!

[MathIzzzFun]

peggy:

avell:

Dear all


Pls help me for the following questions:-

Qn (1)
4/5 of John's money is equal to 3/8 of Sarah's money. Express Sarah's money as a ratio of John's money in it simplest form (draw a model to help you to solve the sum.

Qn (2)
The ratio of boys and girls on a school bus was 2 : 3. When 16 girls alighted from the bus, the ratio of the remaining boys to girls became 6:5. Find the number of children who remained on the bus.

Hi,

Any MD please? I'm quite lost!

Hi

Here's the MD for Q1 & Q2.



http://postimage.org/image/290mem8sk/


http://postimage.org/image/g4imrx0k/

cheers.

[peggy]

MathIzzzFun,


Many thanks !


Regards,
peggy

[MathIzzzFun]

peggy:

MathIzzzFun,


Many thanks !


Regards,
peggy

Hi peggy,

avec plaisir :lol:

cheers.

[JadeDry]

Good Day.


I have come across \"rules\" in a Textbook, and am a little confused as to how they work:

The sum of the Interior Angles of an N-sided Polygon is-

(n-2) x 180

OR (n-2) x 2 rt, angle S,

OR (2n-4) rt, Angle S.

I would appreciate being advised under what circumstances you apply the second and third rules, as well as what RT and Angle S mean.

Thanks in advance.

[JadeDry]

Good Day.


I would appreciate it if someone could check whether my working is correct on the following Question:

A Polygon has N-sides. One of It's Interior angles is 126 degrees, while the other angles are each equal to 162 degrees, find the value of N.

My working:

Sum of Exterior Angles of a Polygon= 360 degrees.

Therefore: Largest Exterior angle = 180-126= 54 degrees.

Smallest Exterior angle= 180-162=18 degrees.

360-54= 306

306/18= 17 =(N-1) sides

therefore the Polygon has 18 sides.

Is this correct?

Thanks in advance.

[tianzhu]

JadeDry:

Good Day.


I have come across \"rules\" in a Textbook, and am a little confused as to how they work:

The sum of the Interior Angles of an N-sided Polygon is-

(n-2) x 180

OR (n-2) x 2 rt, angle S,

OR (2n-4) rt, Angle S.

I would appreciate being advised under what circumstances you apply the second and third rules, as well as what RT and Angle S mean.

Hi

Are these formulae from primary maths books?

If you keen to find out more, please follow this link.
http://www.mathsteacher.com.au/year8/ch10_geomcons/02_internal/anglesum.htm

Best wishes

[CoffeeCat]

JadeDry:

Good Day.


I would appreciate it if someone could check whether my working is correct on the following Question:

A Polygon has N-sides. One of It's Interior angles is 126 degrees, while the other angles are each equal to 162 degrees, find the value of N.

My working:

Sum of Exterior Angles of a Polygon= 360 degrees.

Therefore: Largest Exterior angle = 180-126= 54 degrees.

Smallest Exterior angle= 180-162=18 degrees.

360-54= 306

306/18= 17 =(N-1) sides

therefore the Polygon has 18 sides.

Is this correct?

Thanks in advance.

Yes, you are absolutely correct!