Q&A - PSLE Math

[MathIzzzFun]

Angel25:

Pei Chuan Public School Prelim 2011 P2 Q18


At first, Ella had $52 more than Felix. After Ella had spent 25% of her money and Felix had spent 3/5 of his, Ella had $123 more than Felix. How much money did Ella have at first?

Hi

You can solve this using MD too.. I am using the units method here as I do not time to draw the model...

Felix = 20u
Ella = 20u + 52

Ella spent 25%, had 3/4 left --> 15u + 39
Felix spent 3/5, had 2/5 left --> 8u

So, 15u + 39 = 8u + 123, 7u = 84, 1u = 12

At first, Ella had 20u + 52 = $292

cheers.

[MathIzzzFun]

Angel25:

CHIJ Prelims 2011 P2 Q12


At 8.30am, Myke and Jerome set off at the same time from Town X to Town Y. At 11.00am, Myke completed his journey but Jerome had covered only 5/8 of the journey. Jerome's speed was 54km/h slower than Myke's.

a) Find the distance between Town X and Town Y.
b) At what time would Jerome complete his journey?

Hi

8.30am --> 11.00am = 2.5h, Myke reached Town Y in 2.5h.
2.5h x 54km = 135 km --> Jerome was still 135 km from Town Y at 11.00am
so 3/8 of the distance = 135 km, distance between Town X & Y = 135/3 x 8 = 360 km

Jerome took 2.5h to cover 5/8 of the distance, for remaining 3/8 of the distance, time taken = 3/5 x 2.5 = 1.5h = 1h 30 min

Jerome will reach Town Y at 11.00 am + 1h 30min = 12.30 pm

cheers.

[tianzhu]

Hi


HP 2011 SA2 Q11

Outer fence ----- 40cm
Inner fence ------ 180cm

Use a common length of 360cm as comparison

Inner fence ------- 2180 ------- 18 metal spokes
Outer fence ------- 940 --------27 wooden spokes
Difference ------- 9 wooden spokes

198/9 -------22
22(18+27) ------- 990

Best wishes

[tianzhu]

Hi


CHIJ 2011 Prelims P2 Q15

You may solve it using MD.

Donovan ----- 1 unit + 48

Ethan ------1 unit

Freddy ------ 2 units

Gilbert ------- 432

1 unit + 48 -------20%
4 units + 192 ------ 80%

4 units + 192 -------- 3 units + 432

1 unit ------- 240

Total number of trading cards -------- 4 units + 48 + 432 --------1440

487 – (240+48) -------199

199/288* 100% --------- 69.1%

Best wishes

[MathIzzzFun]

Angel25:

http://i53.tinypic.com/sfey6o.jpg\"> http://i53.tinypic.com/sfey6o.jpg\"> Henry Park 2011 Prelim P2 Q11

Hi

every 360cm stretch,
Number of metal spokes = 9 x 2 = 18
Number of wooden spokes = 3 x 9 = 27
27 – 18 = 9 --> 9 more wooden spokes than metal spokes every 360cm.
198 ÷ 9 = 22 of 360 cm-stretch
Number of metal spokes = 22 x 18 = 396
Number of wooden spokes = (22 x 27) x 4 = 2376
2376 + 396 = 2772
There a total of 2772 wooden and metal spokes.


cheers.

[tianzhu]

Angel25:

http://i52.tinypic.com/10ruv0z.jpg\"> Henry Park 2011 Prelim P2 Q10

Hi

Rearrange the figure.

Area of square (12*12) ------ area of circle (r6) -------- A

Area of eye -------- area of semi circle (r6) – square (6*6) -------- B

The answer is (A+B)

I’ll leave it to students to work out the calculations

Best wishes

[Alchemist]

Hi - Could someone h http://i56.tinypic.com/9tcx1t.jpg\"> elp me with the sum below.

[Daddy]

Hi,


Need help!! Thanks

A group of boys tool their pets to a park. Each boy either has a dog or cat. Between the boys and theirs pets, there were a total of 204 leags.
a) How many boys were there?
b) If there were 15 cats, how many more dogs than cats were there?

Thanks all the masters

[Alchemist]

Daddy:

Hi,


Need help!! Thanks

A group of boys tool their pets to a park. Each boy either has a dog or cat. Between the boys and theirs pets, there were a total of 204 leags.
a) How many boys were there?
b) If there were 15 cats, how many more dogs than cats were there?

Thanks all the masters

Every group of Boy + Cat/Dog will have 6 legs.
So total no of such groups - 204/6 = 34.

Therefore a) 34 boys

b) If there were 15 cats - there are 19 dogs. So 4 more dogs than cats.

Am I missing something here?

[tianzhu]

vidhyalog:

Hi - Could someone h http://i56.tinypic.com/9tcx1t.jpg\"> elp me with the sum below.

Hi

Draw a bigger square such that the circle is inscribed in it.

This bigger square is twice the area of the smaller square (8)

Area of big square ------ 8*2 -----16
Length of 1 side of big square -------4

Radius of circle ------- 2cm

Best wishes