Q&A - PSLE Math

[Brenda10]

zsqchx:

Please Help!Thanks


Jerry bought four times as many pencils as notebooks and spent a total of $21.60. He spent $2.40 more on the notebooks than the pencils. Given that a notebook costs $3.20 more than a pencil. find the cost of a pencil.

Hi, this quesiton look familar! May I know is from which prelim paper ?

[pixiedust]

Let me give it a try :


Jerry bought four times as many pencils as notebooks and spent a total of $21.60. He spent $2.40 more on the notebooks than the pencils. Given that a notebook costs $3.20 more than a pencil. find the cost of a pencil.

spent on pencils = $9.60
spent on notebooks = $12

4U pencils -> $9.60
1U notebook -> $12
1U pencils -> $2.40

$12-$2.4=$9.60
$9.60/$3.20=3

3 notebooks -> $12, each -> $4
cost of each pencil = $0.80

check :
3 notebooks * $4 = $12
12 pencils * $0.80 = $9.60

[tianzhu]

kavisuresh:

Pls help to solve.

1. There are ___ hundredths in 186.42

2. Gerald had $20 more than Tommy at first. After Gerald gave Tommy $60, Gerald had 1/3 as much money as Tommy. Find amt of money Gerald had at first ?

3. Krishnan spent $84 on some plates and 1/3 of remaining money on some cups. If he had 1/5 of original sum of money left, how much did she have at first ?

Hi

Due to time constraints, I’ll give you some pointers instead of drawing models.

Q1) 18642

Q2) You may use MD.

I’ll give you the end MD.

Gerald ------ 1 unit + 40 +20
Tommy ------ 1 unit + 40 +20 + 40 which is equal to 3 times or 3 units.

2 units --------100
1 unit -------50

Gerald -------110 at first.


Q3) You may use MD.

Draw a bar, cut 1 portion to show $84, subdivide the remaining part into 3 small units.

1 unit ------cup
2 units ------left

2 units ------1/5 of original
10 units ------ original sum of money

Hence 7 units ------ 84
1 unit ------- 12

10 units -------120

Best wishes

[zsqchx]

pixiedust:

Let me give it a try :


Jerry bought four times as many pencils as notebooks and spent a total of $21.60. He spent $2.40 more on the notebooks than the pencils. Given that a notebook costs $3.20 more than a pencil. find the cost of a pencil.

spent on pencils = $9.60
spent on notebooks = $12

4U pencils -> $9.60
1U notebook -> $12
1U pencils -> $2.40

$12-$2.4=$9.60
$9.60/$3.20=3

3 notebooks -> $12, each -> $4
cost of each pencil = $0.80

check :
3 notebooks * $4 = $12
12 pencils * $0.80 = $9.60

Thank you very much!

[zsqchx]

Brenda10:

zsqchx:

Please Help!Thanks


Jerry bought four times as many pencils as notebooks and spent a total of $21.60. He spent $2.40 more on the notebooks than the pencils. Given that a notebook costs $3.20 more than a pencil. find the cost of a pencil.

Hi, this quesiton look familar! May I know is from which prelim paper ?

Catholic High 2011 prim Q16

[smileplease]

Need help on this Q :


Mr Samad made some toys to sell. He sold 20% of the toys on Monday. He sold 27 toys on Tuesday. On Wednesday he sold 10% of the remaining toys. After that he found that the toys he had left was 1 more than 1/2 the number of toys he had made. How many toys did he made?

thank you.

[ck123]

Hi can confirm question 15 of nanyang prelim 2011 answer is 428 2/3 mins or 428 4/7 mins

Thanks

[smileplease]

It should be 428 2/3 mins. This part is tricky, this is the detailed solution my friend gave me.


Vol of tank = 3x3x15 = 13.5 m3 x1000 = 13,500 l
Vol of water = 1/3 x 13.5 =4.5 m3 x1000 = 4500l
13500 – 4500 = 9000 l
2min => water filled = 18x2 = 36l +6l = 42l
9000 / 42 = 214 12/42 = 214 2/7 of 2 min
214x2 =428min , water filled = 42 x 214 =8988 l
9000 – 8988 =12l
1min =18l
12l = 1/18 x12 = 2/3 min
Total time taken = 428 + 2/3 = 428 2/3 min

[ck123]

:thankyou: smileplease got it

[tianzhu]

smileplease:

Mr Samad made some toys to sell. He sold 20% of the toys on Monday. He sold 27 toys on Tuesday. On Wednesday he sold 10% of the remaining toys. After that he found that the toys he had left was 1 more than 1/2 the number of toys he had made. How many toys did he made?

Hi

Mon ------- 2 units
The remaining 8 units is subdivided into 27 (Tues) + 1 part (Wed) + 9 parts left.

8 units – 27 ------ 10 parts -------E1
5 units + 1 ------ 9 parts ------- E2

Multiply E1 by 9 and E2 by 10

72 units – 243 ------ 90 parts
50 units + 10 ------- 90 parts

22 units --------253
1 unit ------- 11.5

10 units ------ 115.

Best wishes

PS ------ The total number of 115 is a whole number which looks logical. However base on this figure, the number of toys sold on Wed is 6.5, which doesn’t seem right. Please check with the source of your question.