Hi Lizawalizawa wrote:Hi Tianzhu,

Your answer is correct. My son has tried this paper before. But I remembered our answer key did have the correct answer.

Lizawa

Thanks, appreciate it if you could share your solution.

Academic support for Primary 6 and PSLE

Post
by **lizawa** » Tue Jul 15, 2008 10:47 am

Large packet

c:s:t

= 1:2:3

Standard packet

c:s

4:5

Large packet contains 2x as many candies as standard packet.

No. of units (standard packet) = 9

no. of units (large packet) = 9 *2 = 18

therefore, c:s:t = 3:6:9

(a) 1 standard + 1 large, c:s:t = 7:11:9

(b)

before eating : c:s:t = 7:11:9

after eating 21 candies, c:s:t = 2:3:3 = 6:9:9

No toffee candies are eaten

18u - 15u = 21

3u = 21

u =7

candies left = 24*7 = 168.

c:s:t

= 1:2:3

Standard packet

c:s

4:5

Large packet contains 2x as many candies as standard packet.

No. of units (standard packet) = 9

no. of units (large packet) = 9 *2 = 18

therefore, c:s:t = 3:6:9

(a) 1 standard + 1 large, c:s:t = 7:11:9

(b)

before eating : c:s:t = 7:11:9

after eating 21 candies, c:s:t = 2:3:3 = 6:9:9

No toffee candies are eaten

18u - 15u = 21

3u = 21

u =7

candies left = 24*7 = 168.

Post
by **lizawa** » Thu Jul 17, 2008 10:25 am

Solution

Total area of cirlces

(B+C) : A

= 4:5

= 24:30

1/6 of A shaded -> 1/6 * 30 = 5 units shaded

unshaded A -> 30 units - 5 units = 25 units

unshaded (B+C) -> 24 - 5 = 19 units

Can draw model here, to see clearer.

B has 5 units, C has 3 units. Size of units in B and C are different.

5 units of B + 3 units of C -> 24

1 unit of B + 1unit of C -> 5

3 units of B + 3 units of C ->15

2 units of B -> 24 - 15 = 9

unshaded B = 4 units of B -> 9 * 2 = 18

2 units of C -> 24 - 18 - 5 = 1

unshaded C = 2 units = 1

unshaded

A:B:C

= 25:18:1

Total area of cirlces

(B+C) : A

= 4:5

= 24:30

1/6 of A shaded -> 1/6 * 30 = 5 units shaded

unshaded A -> 30 units - 5 units = 25 units

unshaded (B+C) -> 24 - 5 = 19 units

Can draw model here, to see clearer.

B has 5 units, C has 3 units. Size of units in B and C are different.

5 units of B + 3 units of C -> 24

1 unit of B + 1unit of C -> 5

3 units of B + 3 units of C ->15

2 units of B -> 24 - 15 = 9

unshaded B = 4 units of B -> 9 * 2 = 18

2 units of C -> 24 - 18 - 5 = 1

unshaded C = 2 units = 1

unshaded

A:B:C

= 25:18:1

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