Q&A - PSLE Math

[superksmum]

MathIzzzFun:

superksmum:

Hi can someone please help on these 2 questions:


2) Primary 6A has 30 pupils while Primary 6B has 35 pupils. The pupils in both classes took the same Math Test and they scored an average of 80 marks. The average score of Primary 6A was 13 marks lower than that of Primary 6B. find the average score of Primary 6A.

Thank you.

http://i34.tinypic.com/npnw8x.png\">

cheers.

:thankyou:

[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.