Q&A - PSLE Math

[ozora]

tianzhu:

ozora:

Need help:

q1) Doreen n Joyce started jogging at 7 am round 400m track. Doreen stopped jogging at 7.20am. By then, Joyce covered 2/3 of the distance completed by Doreen. Doreen ave speed was 30m/min faster than Joyce. How many rounds of track had each of them completed?

Hi

Distance ratio

Doreen:Joyce ---- 3:2

Speed ratio

Doreen:Joyce ---- 3:2

1 unit ------ 30 m/min

Doreen’s speed ------- 3*30 ------ 90 m/min

Joyce’s speed -------- 60 m/min

In 20 minutes

Doreen ------- 90*20 ------- 1800

1800/400 ------- 4 ½ rounds

Joyce -------- 60*20 ------- 1200

1200/400 ------- 3 rounds

Best wishes

thanks for teaching alt method

[ozora]

Need help in speed question.

The distance between town A and town B is 180km.
A van travelled from Town A at 1130am to town B.
1/2h later, a car travelled from town A to town B at an average speed of 75km/h.
The car overtook the van and reached town B first. The van reached town B at 2.30pm.
A) at what time did the car overtake the van?
B) how far away was the van from town B when the car reached town B?

[Oldschool]

ozora:

Need help in speed question.

The distance between town A and town B is 180km.
A van travelled from Town A at 1130am to town B.
1/2h later, a car travelled from town A to town B at an average speed of 75km/h.
The car overtook the van and reached town B first. The van reached town B at 2.30pm.
A) at what time did the car overtake the van?
B) how far away was the van from town B when the car reached town B?

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 (2.4+0.5) hrs, the Van travelled = 60 x (2.9) = 174km

Thus, the Van is 180-174=6 km away from B


Note: My error for 2nd part, instead of 2.4, it should be 2.9hrs


Regards

[ozora]

Oldschool:

ozora:

Need help in speed question.

The distance between town A and town B is 180km.
A van travelled from Town A at 1130am to town B.
1/2h later, a car travelled from town A to town B at an average speed of 75km/h.
The car overtook the van and reached town B first. The van reached town B at 2.30pm.
A) at what time did the car overtake the van?
B) how far away was the van from town B when the car reached town B?

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

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

[Oldschool]

ozora:

Oldschool:

[quote=\"ozora\"]Need help in speed question.

The distance between town A and town B is 180km.
A van travelled from Town A at 1130am to town B.
1/2h later, a car travelled from town A to town B at an average speed of 75km/h.
The car overtook the van and reached town B first. The van reached town B at 2.30pm.
A) at what time did the car overtake the van?
B) how far away was the van from town B when the car reached town B?

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

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

[ozora]

Oldschool:

ozora:

Need help in speed question.

The distance between town A and town B is 180km.
A van travelled from Town A at 1130am to town B.
1/2h later, a car travelled from town A to town B at an average speed of 75km/h.
The car overtook the van and reached town B first. The van reached town B at 2.30pm.
A) at what time did the car overtake the van?
B) how far away was the van from town B when the car reached town B?

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 (2.4+0.5) hrs, the Van travelled = 60 x (2.9) = 174km

Thus, the Van is 180-174=6 km away from B


Note: My error for 2nd part, instead of 2.4, it should be 2.9hrs


Regards

thanks

[YumYum]

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


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

[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 John spent as a ratio of the amount John saved. thks!

[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.

[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 John spent as a ratio of the amount John saved. thks!

pls check the last sentence --- I think it is probably
Express the amount of money Derrick spent as a ratio of the amount John saved.

or

Express the amount of money John spent as a ratio of the amount Derrick saved..

cheers.