Q&A - PSLE Math

[YumYum]

MathIzzzFun:

YumYum:

Hi, can someone pls help with this Qn? thanks!


http://i34.tinypic.com/121fyih.jpg\">

unshaded area = 1/3 area of original rectangle.
shaded area = 1/3 area of original rectangle = 28 cm2

area of original rectangle = 84 cm2

cheers.

Thanks for yr usual help

[ozora]

help needed. looks simple but my answer is fraction which must be wrong.

Tom had 295 more sweets than John.
After Tom gave away 2/5 of the sweets he had and John gave away 2/3 of the sweets, Tom had 329 more sweets than John.
how many sweets did they have altogether at first?

[ozora]

Hi,


Speed of Van = 180 / 3 = 60km/h

a) At the time of overtaking, both Van and Car have travelled the same distance,

60(t) = 75 (t - 1/2)
t = 2.5 hrs

So, the time is 1400 hrs or 2pm when the Car overtakes the Van.

b) Time taken for Car to reach B = 180 / 75 = 2.4hrs

In 2.4hrs, the Van travelled = 60 x 2.4 = 144km

Thus, the Van is 180-144=36 km away from B

Regards[/quote] thanks got it correct the first part but should the answer in b) 6 km as the van has travelled extra of 0.5h[/quote]


Hi,

Yep, for Part (B), you are correct.

Thanks[/quote]
thanks but without your guide, i also got stuck

[ozora]

ozora:

help needed. looks simple but my answer is fraction which must be wrong.

Tom had 295 more sweets than John.
After Tom gave away 2/5 of the sweets he had and John gave away 2/3 of the sweets, Tom had 329 more sweets than John.
how many sweets did they have altogether at first?

I redo the model.
is Tom's sweets = 523
and John's sweets = 228.
can anyone check if my answer is correct.

[Oldschool]

ozora:

ozora:

help needed. looks simple but my answer is fraction which must be wrong.

Tom had 295 more sweets than John.
After Tom gave away 2/5 of the sweets he had and John gave away 2/3 of the sweets, Tom had 329 more sweets than John.
how many sweets did they have altogether at first?

I redo the model.
is Tom's sweets = 523
and John's sweets = 228.
can anyone check if my answer is correct.

Hi,

Nope.

Maybe you want to change to LCM of 5 and 3, which is 15 for easier approach.

Regards

[php]

ozora:

ozora:

help needed. looks simple but my answer is fraction which must be wrong.

Tom had 295 more sweets than John.
After Tom gave away 2/5 of the sweets he had and John gave away 2/3 of the sweets, Tom had 329 more sweets than John.
how many sweets did they have altogether at first?

I redo the model.
is Tom's sweets = 523
and John's sweets = 228.
can anyone check if my answer is correct.

Using LCM 5,3 i.e. 15

Before
Tom -> 15units + 295
John -> 15units

Gave Away
Tom -> 2/5 (15units + 295) = 6units + 118
John -> 2/3 (15units) = 10units

Left
Tom -> 15units+295-6units-118 = 9units + 177
John -> 15units - 10units = 5 units

9units+177 - 5units = 329
4units = 152
1unit = 38

15units+295+15units = 38x30 + 295 = 1435

[MathIzzzFun]

YumYum:

Hi, one more Qn:


Derrick and John shared a sum of money.
Derrick received 2/7 of the sum of money.
Both of them spent part of their money and saved the rest.
The amount of money Derrick spent was 3/5 the amount he saved.
The amount of money John spent was 1/9 the amount he saved.
Express the amount of money Derrick spent as a ratio of the amount John saved. thks!

Derrick's money : John's money = 2 : 5 --> 8u : 20u

Derrick's spending : Derrick's savings --> 3u : 5u
John's spending : John's savings --> 2u : 18u

Derrick's spending : John's savings = 3u : 18u = 1 : 6

cheers.

[ozora]

php:

ozora:

[quote=\"ozora\"]help needed. looks simple but my answer is fraction which must be wrong.

Tom had 295 more sweets than John.
After Tom gave away 2/5 of the sweets he had and John gave away 2/3 of the sweets, Tom had 329 more sweets than John.
how many sweets did they have altogether at first?

I redo the model.
is Tom's sweets = 523
and John's sweets = 228.
can anyone check if my answer is correct.

Using LCM 5,3 i.e. 15

Before
Tom -> 15units + 295
John -> 15units

Gave Away
Tom -> 2/5 (15units + 295) = 6units + 118
John -> 2/3 (15units) = 10units

Left
Tom -> 15units+295-6units-118 = 9units + 177
John -> 15units - 10units = 5 units

9units+177 - 5units = 329
4units = 152
1unit = 38

15units+295+15units = 38x30 + 295 = 1435[/quote]Saw my mistakes. thanks

[Suz855]

Need help with following speed qns


Q1) A car started travelling from Town A to Town B at 9a.m. At the same time, the lorry started travelling from Town B to Town A. The car had a speed of 20km/h faster than the lorry. The car passed the lorry 45km away from the midpoint. Given that the car reached Town B at 3p.m., what time would the lorry reached Town A? :?

Q2) At 11a.m., Mr T left from Town X & drove towards Town Y at an ave speed of 80km/h. 15 min later, Mr R left Town Y and drove along the same route as Mr T towards Town X. After travelling 120km, Mr R passed Mr T.
a) What was the ave speed at which Mr R travelled?
b) How far apart were there at 3.20p.m.? Express your answer as a fraction.
:sad: :imdrowning: :frustrated:




Thanks

[MathIzzzFun]

Suz855:

Need help with following speed qns


Q1) A car started travelling from Town A to Town B at 9a.m. At the same time, the lorry started travelling from Town B to Town A. The car had a speed of 20km/h faster than the lorry. The car passed the lorry 45km away from the midpoint. Given that the car reached Town B at 3p.m., what time would the lorry reached Town A? :?

Q2) At 11a.m., Mr T left from Town X & drove towards Town Y at an ave speed of 80km/h. 15 min later, Mr R left Town Y and drove along the same route as Mr T towards Town X. After travelling 120km, Mr R passed Mr T.
a) What was the ave speed at which Mr R travelled?
b) How far apart were there at 3.20p.m.? Express your answer as a fraction.
:sad: :imdrowning: :frustrated:

Thanks

Q1- The car reached Town B at 3 pm or 5 pm ?
If the car reached at 3 pm, then the speeds for car and lorry are not realistic --> 30 km/h for car and 10 km/h for lorry.

Q2 - is the question complete ? any info left out - eg, at what time did Mr T and Mr R pass each other ? or Mr R is also travelling in the same direction ie from X to Y?

cheers.