## Q&A - PSLE Math

### Re: Q&A - PSLE Math

Thanks in advance for the help.

Sally bought some chocolates and gave half of them to Mabel. Sally also bought some lollipops and gave half of them to Mabel. Mabel ate 7 lollipops and Sally ate 16 chocolates.

After that, the number of lollipops and chocolates Mabel had were in the ratio 1:8 and the number of lollipops and chocolates Sally had were in the ratio 1:5. How many lollipops did Sally buy at first?

Answer says 48 but I could not understand how to arrive at it.

Sally bought some chocolates and gave half of them to Mabel. Sally also bought some lollipops and gave half of them to Mabel. Mabel ate 7 lollipops and Sally ate 16 chocolates.

After that, the number of lollipops and chocolates Mabel had were in the ratio 1:8 and the number of lollipops and chocolates Sally had were in the ratio 1:5. How many lollipops did Sally buy at first?

Answer says 48 but I could not understand how to arrive at it.

### Re: Q&A - PSLE Math

Make the denominator the same first.voltes5 wrote:Need help please...could not understand the answer sheet.

Patricia baked 120 more cupcakes than muffins. She sold 5/6 of the cupcakes and 1/5 of muffins. In the end she had 75 more muffins than cupcakes left. How many cupcakes and muffins did she bake at first?

5/6 sold would be 25/30 sold.

1/5 sold would be 6/30 sold

Move on to the model.

CUPCAKE [25u sold][5u left][120]

MUFFINS [6u sold][24u left]

120 x 5/6 = 100

120 x 1/6 = 20

MODEL ON WHAT'S LEFT

CUPCAKE [5u left][20]<----75---->

MUFFINS [----------24u left----------]

Let's equate.

5u + 20 = 24u - 75

24u-5u = 75+20

19u = 95

1u = 5

5 x 60u + 120 = 300+120

= 420

Answer: 420

Solved by DS

### Re: Q&A - PSLE Math

Need help in this question. Could I assume that EG =EF?

Last edited by ozora on Sun Sep 27, 2015 1:17 am, edited 2 times in total.

### Re: Q&A - PSLE Math

Similar to 2009 PSLE mathematics question.voltes5 wrote:Thanks in advance for the help.

Sally bought some chocolates and gave half of them to Mabel. Sally also bought some lollipops and gave half of them to Mabel. Mabel ate 7 lollipops and Sally ate 16 chocolates.

After that, the number of lollipops and chocolates Mabel had were in the ratio 1:8 and the number of lollipops and chocolates Sally had were in the ratio 1:5. How many lollipops did Sally buy at first?

Answer says 48 but I could not understand how to arrive at it.

Let's start by doing it backwards.

Mabel

L[]

c[][][][][][][][][16]

Sally

L [][7]

C [][7][][7][][7][]7][][7]

Reason why there is an extra 7 is because Sally didnt eat 7 lollipop.

Reason Why there is an extra 16 is because Mabel didn't eat 16 chocolate.

Let's equate.

8u - 16 = 5u + 7x5

8u - 16 = 5u + 35

3u = 35+16

1u = 17

17 + 7 = 24

24X 2= 48

Answer:

**48**

Solved by DS.

### Re: Q&A - PSLE Math

Yes, △EHJ = △FJG. It's not an assumption..ozora wrote:Need help in this question.

cCould I assume that EHJ=FJG?

there fore the answer is 324cm2?

△EHG = △FHG. Both have the same base and Height.

Therfore △EHJ = △EHG - △GHJ

and △FJG = △FHG - △GHJ

- alfretztay
- KiasuGrandMaster
**Posts:**1199**Joined:**Sun Sep 12,**Total Likes:**5

### Re: Q&A - PSLE Math

Area of △EFJ = (1/2) x 48 x 18 = 432 sq cmozora wrote:Need help in this question. Could I assume that EG =EF?

Area of △EFJ = (4/7) x Area of 4-sided fig EFHK

Area of 4-sided fig EFHK = (432 x 7)/4 = 756

Area of △EFH = Area of △EFG (same base and height)

Area of △FGJ = Area of △EHJ

Total area of shaded part = 756 - 432 = 324

Ans : 324 sq cm

- alfretztay
- KiasuGrandMaster
**Posts:**1199**Joined:**Sun Sep 12,**Total Likes:**5

### Re: Q&A - PSLE Math

I would solve the above problem as follows :NerdyMath wrote:Similar to 2009 PSLE mathematics question.voltes5 wrote:Thanks in advance for the help.

Sally bought some chocolates and gave half of them to Mabel. Sally also bought some lollipops and gave half of them to Mabel. Mabel ate 7 lollipops and Sally ate 16 chocolates.

After that, the number of lollipops and chocolates Mabel had were in the ratio 1:8 and the number of lollipops and chocolates Sally had were in the ratio 1:5. How many lollipops did Sally buy at first?

Answer says 48 but I could not understand how to arrive at it.

Let's start by doing it backwards.

Mabel

L[]

c[][][][][][][][][16]

Sally

L [][7]

C [][7][][7][][7][]7][][7]

Reason why there is an extra 7 is because Sally didnt eat 7 lollipop.

Reason Why there is an extra 16 is because Mabel didn't eat 16 chocolate.

Let's equate.

8u - 16 = 5u + 7x5

8u - 16 = 5u + 35

3u = 35+16

1u = 17

17 + 7 = 24

24X 2= 48

Answer:48

Solved by DS.

For chocolate,

Sally : 2u - 1u - 16 = 1u - 16

Mabel : +1u

For lollipops,

Sally : 2p - 1p = 1p

Mabel : +1p - 7

For Mabel,

(1p - 7) x 8 ------- 1u

8p - 56 ------- 1u

For Sally,

1p x 5 ------- 1u - 16

5p + 16 ------- 1u

8p - 56 ------- 5p + 16

3p ------- 72

1p ------- 72/3 = 24

2p ------- 2 x 24 = 48

Ans : 48 lollipops.

Last edited by alfretztay on Sun Sep 27, 2015 5:06 pm, edited 1 time in total.

- alfretztay
- KiasuGrandMaster
**Posts:**1199**Joined:**Sun Sep 12,**Total Likes:**5

### Re: Q&A - PSLE Math

I would solve the above problem as follows :NerdyMath wrote:Make the denominator the same first.voltes5 wrote:Need help please...could not understand the answer sheet.

Patricia baked 120 more cupcakes than muffins. She sold 5/6 of the cupcakes and 1/5 of muffins. In the end she had 75 more muffins than cupcakes left. How many cupcakes and muffins did she bake at first?

5/6 sold would be 25/30 sold.

1/5 sold would be 6/30 sold

Move on to the model.

CUPCAKE [25u sold][5u left][120]

MUFFINS [6u sold][24u left]

120 x 5/6 = 100

120 x 1/6 = 20

MODEL ON WHAT'S LEFT

CUPCAKE [5u left][20]<----75---->

MUFFINS [----------24u left----------]

Let's equate.

5u + 20 = 24u - 75

24u-5u = 75+20

19u = 95

1u = 5

5 x 60u + 120 = 300+120

= 420

Answer: 420

Solved by DS

Cupcakes ------- 6u - 5u = 1u

Muffins ------ 5p - 1p = 4p

6u - 5p ------- 120

4p - 1u ------- 75

1u ------- 4p - 75

6(4p - 75) - 5p ------- 120

19p ------ 570

1p ------- 570/19 = 30

5p ------- 5 x 30 = 150 (muffins)

1u ------- 4 x 30 - 75 = 45

6u ------- 6 x 45 = 270 (cupcakes)

270 + 150 = 420 (cupcakes and muffins)

Ans : 420 cupcakes and muffins.

### Re: Q&A - PSLE Math

Appreciate any help on this one...

Jun Kee had some bags of nails. The average number of nails in each bag was 146. After Jun Kee added another bag containing 128 nails, the average number of nails in each bag became 143. How many bags of nails were there after the new bag was added?

Jun Kee had some bags of nails. The average number of nails in each bag was 146. After Jun Kee added another bag containing 128 nails, the average number of nails in each bag became 143. How many bags of nails were there after the new bag was added?

### Re: Q&A - PSLE Math

Average difference -- > 146-143=3voltes5 wrote:Appreciate any help on this one...

Jun Kee had some bags of nails. The average number of nails in each bag was 146. After Jun Kee added another bag containing 128 nails, the average number of nails in each bag became 143. How many bags of nails were there after the new bag was added?

143-128 = 15

15/3 = 5

5 + 1 = 6.

Answer:

**6**

Solved by DS.