Q&A - PSLE Math

[superksmum]

Hi can someone please help on these 2 questions:


1) Alan and Charlie received some money from their mother. Charlie would have $32 more than Alan if Alan gave 2/5 of his share to Charlie. Charlie would have $96 more than Alan if Alan gave 2/3 of his share to Charlie. How much money did they receive from his mother?

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.

[MathIzzzFun]

superksmum:

Hi can someone please help on these 2 questions:


1) Alan and Charlie received some money from their mother. Charlie would have $32 more than Alan if Alan gave 2/5 of his share to Charlie. Charlie would have $96 more than Alan if Alan gave 2/3 of his share to Charlie. How much money did they receive from his mother?


Thank you.

At first, Alan's money --> 15 units (LCM of 3 &5)

If Alan gave 2/5 of his money = 6 units, to Charlie, Charlie would have $32 more than Alan:

Alan's money left --> 9 units
Charlie's money left --> 9 units + $32

At first,
Charlie's money --> 3 units +$32
Alan's money --> 15 units

If Alan gave 2/3 of his share = 10 units, to Charlie, Charlie would have $96 more than Alan,

Alan's money left --> 5 units
Charlie's money --> 13 units + $32

13 units + $32 = 5 units + $96
8 units --> $64, 1 unit --> $8

Charlie's money --> 3 x $8 $32 = $56
Alan's money --> 15 x $8 = $120

cheers.

[superksmum]

MathIzzzFun:

superksmum:

Hi can someone please help on these 2 questions:


1) Alan and Charlie received some money from their mother. Charlie would have $32 more than Alan if Alan gave 2/5 of his share to Charlie. Charlie would have $96 more than Alan if Alan gave 2/3 of his share to Charlie. How much money did they receive from his mother?


Thank you.

At first, Alan's money --> 15 units (LCM of 3 &5)

If Alan gave 2/5 of his money = 6 units, to Charlie, Charlie would have $32 more than Alan:

Alan's money left --> 9 units
Charlie's money left --> 9 units + $32

At first,
Charlie's money --> 3 units +$32
Alan's money --> 15 units

If Alan gave 2/3 of his share = 10 units, to Charlie, Charlie would have $96 more than Alan,

Alan's money left --> 5 units
Charlie's money --> 13 units + $32

13 units + $32 = 5 units + $96
8 units --> $64, 1 unit --> $8

Charlie's money --> 3 x $8 $32 = $56
Alan's money --> 15 x $8 = $120

cheers.

:thankyou:

[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.

[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