Q&A - PSLE Math

[dingdongrc]

Is the answer to the Enry Park Math Qn 5 = 51.48 cm2?

[dingdongrc]

dingdongrc:

Is the answer to the Enry Park Math Qn 5 = 51.48 cm2?

Sorry, I meant Henry Park Prelims P2 Q10.

[MathIzzzFun]

Angel25:

Pei Chuan 2011 Prelims P2 Q14

http://i54.tinypic.com/alj9sz.jpg\">

Hi

this was discussed in an earlier post ..

http://i55.tinypic.com/rmsmdl.jpg\">

cheers.

[MathIzzzFun]

Angel25:

Pei Chuan 2011 Prelims P2 Q12 http://i55.tinypic.com/6ps1tw.jpg\">

Hi

Draw a diagram to show the journey - it will help to see the problem better.

Let X be the point the motorist passed the taxi. From X, the taxi travelled for 1.5h and was still 25 km away from town A.
So, distance AX (Town A to Point X) = 25 km + 90 km/h x 1.5 h = 160 km

Time taken by motorist to travel distance AX = 4h - 1.5h = 2.5h

The motorist took 4h to travel from Town A to Town B,
distance between Town A & Town B = 4/2.5 x 160 km = 256 km

cheers.

[dingdongrc]

Angel25:

Henry Park Prelim 2011 Q15.


Mr Lee packed some oranges into big boxes and apples into small boxed. Each big box contained 50 oranges and each small box contained 30 apples. After packing, there were 12 more big boxes than small boxes. Given that there were 1240 fewer apples than oranges, how many oranges were there ?

I am a rusty old woman attempting here:

Ratio of packing: Or: Ap = 5 : 3
And Or - Ap = 1240
After packing there are additional 12 x 50 = 600 oranges

Using ratio diff of 5-3 = 2, this equates to the diff of 1240-600 = 640.
2u = 640
1u = 320

Oranges initially = 5 x u +600 = 2220

I did a counter-chcek theerafter to make sure. I need some expert help to exhibit my answers more mathmathically more correctly...these are just logical workings in my brains....

[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.