Q&A - PSLE Math

[Winx5015]

Thanks kiasuaunt and tianzhu. Have a nice weekends

[Shimmer]

Did anyone knows how to solve these questions ?


An empty rectangular tank is being filled with water from Tap A at 1 liter per min. Tap B drains water out from the tank at 800cm cubic per min. How long will it take for the water level to reach a height of 10cm if both the taps are turned on at the same time ?

Mrs Thames took part in a car rally. She had to drive from point a to point b to point c. She drove at a speed of 60km/h from point a to point b which were 20km apart. She took 40 mins to drive from point b to point c which were 50km apart. What was her average speed for the whole journey ?

[pixiedust]

Shimmer:

Mrs Thames took part in a car rally. She had to drive from point a to point b to point c. She drove at a speed of 60km/h from point a to point b which were 20km apart. She took 40 mins to drive from point b to point c which were 50km apart. What was her average speed for the whole journey ?

Question 1 : the base dimension of the tank is missing. is there a picture of the tank with base (length and breadth) ?

Question 2:
Point A to Point B: Distance=20km, Speed=60km/h, Time=1/3hr
Point B to Point Distance=50km, Time=40mins=2/3hr
Total distance=70km, Total Time= 1hr. Average Speed = 70km/hr

[pixiedust]

Need help with (b) Calculate the difference between shaded area 'A' and 'B'.

Thanks !

http://i1197.photobucket.com/albums/aa424/pixie_dust8/mq4.jpg\">

[jewelbox]

How do i solve this psle qn without using guess and check? thks.

A fruit stall sold pears at 70cents each and apples at 40 cents.
Sally bought some pears and Tom bought some apples from the fruit stall.
Sally spent $1.10 more than Tom, but had 7 fruits fewer than Tom.
a) How many pears did Sally buy?
b) how much did tom spend on the apples?

[Shimmer]

pixiedust:

Shimmer:

Mrs Thames took part in a car rally. She had to drive from point a to point b to point c. She drove at a speed of 60km/h from point a to point b which were 20km apart. She took 40 mins to drive from point b to point c which were 50km apart. What was her average speed for the whole journey ?

Question 1 : the base dimension of the tank is missing. is there a picture of the tank with base (length and breadth) ?
Question 2:
Point A to Point B: Distance=20km, Speed=60km/h, Time=1/3hr
Point B to Point Distance=50km, Time=40mins=2/3hr
Total distance=70km, Total Time= 1hr. Average Speed = 70km/hr

Dear pixie dust

Sorry the length is 40cm and breath is 20cm.

By the way, how to upload picture or image to this forum, can anyone give advise.

Thanks

[pixiedust]

Shimmer,


You can check this : http://www.kiasuparents.com/kiasu/forum/viewtopic.php?p=132258#p132258

For your question 1 :
An empty rectangular tank is being filled with water from Tap A at 1 liter per min. Tap B drains water out from the tank at 800cm cubic per min. How long will it take for the water level to reach a height of 10cm if both the taps are turned on at the same time ? Length is 40cm and breath is 20cm.

To reach height of 10cm,
Volume required = 40cm*20m*10cm=8000cm3

In 1 minute,
Tap A adds 1000cm3, Tap B drains 800cm3
Hence, net gain is 200cm3

To reach 8000cm3 -> 8000cm3/200cm3=40minutes

[tianzhu]

pixiedust:

Need help with (b) Calculate the difference between shaded area 'A' and 'B'.

Thanks !

http://i1197.photobucket.com/albums/aa424/pixie_dust8/mq4.jpg\">

Hi

Difference in shaded area ------ Area of circle (r6) – area of triangle (base 10cm and height 12cm)

Divide the above answer by 2 to get (A-B)

Best wishes

[tianzhu]

jewelbox:

How do i solve this psle qn without using guess and check? thks.

A fruit stall sold pears at 70cents each and apples at 40 cents.
Sally bought some pears and Tom bought some apples from the fruit stall.
Sally spent $1.10 more than Tom, but had 7 fruits fewer than Tom.
a) How many pears did Sally buy?
b) how much did tom spend on the apples?

Hi

There are a few approaches to do this question.

There are 7 more apples than pears.

Imagine Sally buying 7 more pears

This will add 7*70 ------ 490 cents

110 + 490 ----- 600

Difference between a pear and an apple ------ 30 cents

Number of apples ------ 600/30 ------ 20

Number of pears ------- 20 - 7 ------ 13

20*0.4 ------- 8 (amount spent on apples)

Best wishes

[Spongy]

tianzhu:

Spongy:

Hi I need help in this question. Please help. Thanks.


1. 500 people paricipated in a contest. 105 of them were adults and the rest were children. 3/5 of boys and 5/7 of the girls were Singaporeans while the rest of the children were foreigners. There were 10 more foreign girls than foreign boys. How many Singaporean children were there?

Hi

This question touches on simultaneous concept.

You may use MD, “Units and Parts” or use letters of the alphabet to show the variables.

Number of children ------- 500 – 105 ------ 395

Boys

Singaporean ------- BBB
Foreigner ------ BB

Girls

Singaporean ------- GGGGG
Foreigner ------ GG

GG ------ BB + 10
G ----- B + 5

BBBBB + BBBBBBBBBBBB + 35 -------- 395 (12B + 35 ------ 395)

B ------ 30
G ------ 35

Number of Singaporean children ----- 90 + 175 ------ 265

Best wishes

Hi Tianzhu, thanks a lot, however I do not understand from
BBBBB + BBBBBBBBBBBB + 35 .......... onwards