Q&A - PSLE Math

[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

[small]

Vanilla Cake, a big thanks..... :celebrate: :celebrate:

[James Ang]

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

Vanilla's answer is standard answer, short and few steps, chance of making mistake is lower.

Shaded area = big quarter circle – triangle
= 1256 - 40x40/2 = 1256 -800
= 456 cm2

[atutor2001]

small:

Question 2:

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

The shaded area = 1 Big quadrant - 2 small squares

The 2 unshaded area in the Big quadrant can be manipulated to form 2 small squares

[small]

Thanks atutor2001, I think my young one’s eyes might not sharp enough. :X

[fxchow]

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.

Hi small,

My girl got answer 15mins for question a but she didn't know for question b. Awaiting for your solution. Thanks