Q&A - PSLE Math

[k1ndan]

[Moderator's note: Topics merged.]


1. Mrs. Tan has drawn up a schedule to have her home cleaned by 3 part-time workers. The cleaner goes to her home once every 3 days, the sweeper once every 4 days and the gardener once every 6 days. If the 3 workers first met on 28 July, when was the earliest date the cleaner has to start work?

2. Mary is meeting a friend at a certain time. If she drives at 80 km/h, she will be 1/3 hour late. If she drives at 60 km/h, she wil be 3/4 hour late. How long will the journey take if she drives at 90 km/h?

[Eagle-Ladybird]

1. 3 days after 28 july i.e. 31 july


2. 1 hr 11mins

[jedamum]

1. Do a search before starting new topic.


2. Mods, please merge with http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=280. TQ.

[Dharma]

Kari:

[Moderator's note: Topics merged.]

After 20 minutes into a cross country race, Teck Seng has run 5/8 of the route while Jack has covered only 3/8 of the distance. Teck Seng runs at the same average speed throughout the race and Jack's average speed is 60 min/min slower than Teck seng's.

a) Find the total distance of the cross country race.

b) If Jack wants to finish the race at the same time as Teck Seng, by how much should he increase his average speed for the remaining part of the race? (Express your answer in m/min)[/img]

http://www.postimage.org/

[Dharma]

finder:

Hi, please help. Thank you.


------------
Ning and Zhongwei jogged to and fro repeatedly along a straight path in a park between two points A and B. Ning jogged at a uniform speed of 4m/s and Zhongwei jogged at a uniform speed of 6m/s. They started jogging from opposite directions at the same time as show below,

A ------------------X-----------------------------------Y--------------------B

They first met one another at point X. The second time they met was at point Y.

a). Given that the distance between X and Y is 160 m. Find the distance between A and B.

b). If they started jogging at 8am, how long did they take to meet again for the third time? (Express your answers in minutes and seconds)

http://www.postimage.org/

http://www.postimage.org/

[small]

Sorry for my ignorance, once again thanks for your help.


Question 1:

Ali had some $10 and $15 cash cards. He sold 1/3 of his cards and collected $3900 from the sales. 2/5 of the cards sold were $10 cash cards.

a) How many $15 cash cards did he sell?

b) How many cash cards did he have left?


Question 2:

http://img9.imageshack.us/img9/8171/scan1n.jpg\">
:oops:

[fxchow]

Hi,


Can anyone help. TIA

At 7.00 a.m, Tim left Town A and headed towards Town B at a uniform speed of 72km/h. Twenty minutes later, Siva left Town B and used the same road to travel to Town A at a uniform speed of 84km/h.
When Tim reached Town B, Siva was still 7km from Town A.

a) How many minutes faster did Siva take to complete his trip than Tim?
b) How long did Siva take to travel from Town B to Town A?

[small]

fxchow:

Hi,


Can anyone help. TIA

At 7.00 a.m, Tim left Town A and headed towards Town B at a uniform speed of 72km/h. Twenty minutes later, Siva left Town B and used the same road to travel to Town A at a uniform speed of 84km/h.
When Tim reached Town B, Siva was still 7km from Town A.

a) How many minutes faster did Siva take to complete his trip than Tim?
b) How long did Siva take to travel from Town B to Town A?

fxchow,

If I did correctly, the answer for your question is:

a) 15mins
b) 1.5 hours

I will post the solution later.

[Vanilla Cake]

small:

Question 1:

Ali had some $10 and $15 cash cards. He sold 1/3 of his cards and collected $3900 from the sales. 2/5 of the cards sold were $10 cash cards.
a) How many $15 cash cards did he sell?
b) How many cash cards did he have left?

Solution
(a)
$10 cash cards : $15 cash cards
2 : 3

10x2 = 20
15x3 = 45

1 'set' = 45+20 = 65
Number of sets = 3900/65 = 60

60 x 3 = 180
Number of cards that Ali sold was 180

(b)
60x5= 300
1u = 300
2u = 600
Number of cash cards that Ali had left was 600

small:

Question 2:
http://img9.imageshack.us/img9/8171/scan1n.jpg\">

Solution
Draw a dotted line to cut the square into half. Draw another dotted line to cut the lower shaded region into half too. Move the two lower shaded regions to fill up the upper shaded region.

Total shaded area of the figure -> Area of quadrant minus area of triangle
(1/4 x 3.14 x 40 x 40) - ( 1/2 x 40 x 40 )
= (1256 - 800) cm2
= 456 cm2

Hope this helps.

[small]

small:

Sorry for my ignorance, once again thanks for your help.


Question 1:

Ali had some $10 and $15 cash cards. He sold 1/3 of his cards and collected $3900 from the sales. 2/5 of the cards sold were $10 cash cards.

a) How many $15 cash cards did he sell?

b) How many cash cards did he have left?


Question 2:

http://img9.imageshack.us/img9/8171/scan1n.jpg\">
:oops:

I manged to solve Q2, left Q1.

http://img9.imageshack.us/img9/6578/scan1j.jpg\">

Yellow area = small square – small quarter circle
= 20 x 20 – ¼ x 20 x 20 x 3.14
= 400 – 314
= 86 cm2

Orange area = ¼ x 20 x 20 x 3.14
= ¼ x 400 x 3.14
= 314 cm2

big quarter circle = ¼ x 40 x 40 x 3.14
= 400 x 3.14
= 1256 cm2

Shaded area = big quarter circle – 2 x Orange area – 2 x yellow area
= 1256 - 628 - 172
= 456 cm2