## Q&A - PSLE Math

### Re: Q&A - PSLE Math

[quote="questionable_i"]Can anyone help me? Thank you in advance.

Q2)

W : B

Meg 7 : 8 , say total is "X" : 7/15X+8/15X-4/15X=132, X=180

given away is 4/15 X = 48 (Ans for a)

Lea 2/3Y:1/3Y , say total is "Y" and white is 2times of black

After receiving 48 black bands from Meg...

Lea 5/9(New Y ie Y+48) : 4/9 (New Y)

Lea : workings on black bands : 1/3Y + 48 = 4/9 (new Y ie Y+48)

1/3Y+48=4/9(Y+48)

(Original) Y=240

(New) Y after receiving 48 from Meg=240+48=288 (Ans for b )

Q2)

W : B

Meg 7 : 8 , say total is "X" : 7/15X+8/15X-4/15X=132, X=180

given away is 4/15 X = 48 (Ans for a)

Lea 2/3Y:1/3Y , say total is "Y" and white is 2times of black

After receiving 48 black bands from Meg...

Lea 5/9(New Y ie Y+48) : 4/9 (New Y)

Lea : workings on black bands : 1/3Y + 48 = 4/9 (new Y ie Y+48)

1/3Y+48=4/9(Y+48)

(Original) Y=240

(New) Y after receiving 48 from Meg=240+48=288 (Ans for b )

### Re: Q&A - PSLE Math

Ans a) 120%=$2400 (Shop A)questionable_i wrote:Can anyone help me? Thank you in advance.

Q3)

therefore 100% = $2000 (shop B)

Ans b) Say Selling Price for A = x% A, SP for B=x%B and discount = 100%-x%

x%B=x%A-$320

$2000(x%)=$2400(x%)-$320

$400(x%)=$320

x%=80%

and the discount will be 100%-80%=20%

### Re: Q&A - PSLE Math

Q1)questionable_i wrote:Can anyone help me? Thank you in advance.

Q1)

Q2)

Q3)

Difference in amount between A and F = $5

Difference in amount in savings = 72-32 = $40

40/5 = 8 weeks

A saved weekly 72/8 = $9 and spent $15

**(a)Hence total money A has per week is 9+15=$24**

(b) F saved $32/8 = $4 per week.

44/4 = 11 weeks

**So F has to save (11-8)= 3 more weeks to buy the watch.**

Q2)

------------------------white-------black

M original--------------7u---------8u

M give 4u B to L-------7u---------8u-4u=4u

L original --------------2p----------p

after rec 4u from M---2p----------p+4u

L New ratio-------------5-----------4

7u+4u->132

11u-> 132

u->12

**(a)So M gave 4 x 12 = 48 to L**

2p/(p+48) -> 5/4

5p+240 -> 8p

3p->240

**(b)Hence L has 3p+48 = 240+48 = 288 beads in the end.**

Q3)

u = price sold by Shop B

1.2u -> 2400

u -> 2000

**(a)Hence shop B is selling the same laptop at $2000**

If x is the % discount by both shops,

(1-x)(2400) = 2000 (1-x) + 320

2400-2400x = 2000-2000x + 320

400x = 80

x = 0.2

**(b)Hence discount is 20%**

### Re: Q&A - PSLE Math

1760 children took part in a run last year. This year, the number of boys increased by 20% while the number of girls decreased by 20%. As a result, the number of girls became twice as many as the number of boys this year.

(a) How many boys took part in the run last year?

(b) What is the percentage decrease in the number of children who took part in the run this year?

(a) How many boys took part in the run last year?

(b) What is the percentage decrease in the number of children who took part in the run this year?

### Re: Q&A - PSLE Math

Someone please help me. Thanks!

A lorry left Town A at 8 a.m. and travelled towards Town B at an average speed of 55 km/h. At 11a.m., a car left Town A for Town B, travelling at an average speed of 85 km/h along the same road. Both the lorry and the car travelled at a uniform speed.

(a) At what time did the car pass the lorry?

(b) How far was the lorry from Town A when the car passed the lorry?

A lorry left Town A at 8 a.m. and travelled towards Town B at an average speed of 55 km/h. At 11a.m., a car left Town A for Town B, travelling at an average speed of 85 km/h along the same road. Both the lorry and the car travelled at a uniform speed.

(a) At what time did the car pass the lorry?

(b) How far was the lorry from Town A when the car passed the lorry?

### Re: Q&A - PSLE Math

Start with boys =5u last year. 5u selected because it's easier to work with a 20% increase.wilburlim wrote:1760 children took part in a run last year. This year, the number of boys increased by 20% while the number of girls decreased by 20%. As a result, the number of girls became twice as many as the number of boys this year.

(a) How many boys took part in the run last year?

(b) What is the percentage decrease in the number of children who took part in the run this year?

This year the boys = 1.2 X 5u = 6u , i.e 20% increasse from 5u

This year the girls= 12u , i.e. twice of boys this year.

Girls this year is 80% of girls last year

80% => 12u

100% => 12u/0.8 = 15u <-last year girls

5u + 15u = 1760

20u =1760

u = 88

a) Last year boys = 5u = 5(88) = 440#

b) Total participants for last year = 20u

Total paticipants for this year = 6u+12u = 18u

Reduce by 2u

% reduction = 2u/20u X 100 = 10% ###

### Re: Q&A - PSLE Math

Lorry had a 3 hr head start, so at 11am the lorry is at a distance of 55 X 3 = 165kmwilburlim wrote:Someone please help me. Thanks!

A lorry left Town A at 8 a.m. and travelled towards Town B at an average speed of 55 km/h. At 11a.m., a car left Town A for Town B, travelling at an average speed of 85 km/h along the same road. Both the lorry and the car travelled at a uniform speed.

(a) At what time did the car pass the lorry?

(b) How far was the lorry from Town A when the car passed the lorry?

a) Car is faster by 85 - 55 = 30km/h

At 11am, the car has to close the gap of 165km, at 30km/h

Time take to close the gap = 165/30 = 5.5 hrs

11am plus 5.5 hr => 4:30 pm #

b)Lorry would have travelled the same distance as the car travelled, so use the car information.

distance when car passed the lorry= 85 X 5.5 = 467.5km #

### Re: Q&A - PSLE Math

Hi, thanks for the reply! But is there a easier way to solve this? I don't understand the 5u for boys at first.Ender wrote:Start with boys =5u last year. 5u selected because it's easier to work with a 20% increase.wilburlim wrote:1760 children took part in a run last year. This year, the number of boys increased by 20% while the number of girls decreased by 20%. As a result, the number of girls became twice as many as the number of boys this year.

(a) How many boys took part in the run last year?

(b) What is the percentage decrease in the number of children who took part in the run this year?

This year the boys = 1.2 X 5u = 6u , i.e 20% increasse from 5u

This year the girls= 12u , i.e. twice of boys this year.

Girls this year is 80% of girls last year

80% => 12u

100% => 12u/0.8 = 15u <-last year girls

5u + 15u = 1760

20u =1760

u = 88

a) Last year boys = 5u = 5(88) = 440#

b) Total participants for last year = 20u

Total paticipants for this year = 6u+12u = 18u

Reduce by 2u

% reduction = 2u/20u X 100 = 10% ###

- questionable_i
- BrownBelt
**Posts:**535**Joined:**Sat Oct 10,**Total Likes:**1

### Re: Q&A - PSLE Math

5u is selected because 20% of 5u is just 1u.. Easier to work.wilburlim wrote:Hi, thanks for the reply! But is there a easier way to solve this? I don't understand the 5u for boys at first.Ender wrote:Start with boys =5u last year. 5u selected because it's easier to work with a 20% increase.wilburlim wrote:1760 children took part in a run last year. This year, the number of boys increased by 20% while the number of girls decreased by 20%. As a result, the number of girls became twice as many as the number of boys this year.

(a) How many boys took part in the run last year?

(b) What is the percentage decrease in the number of children who took part in the run this year?

This year the boys = 1.2 X 5u = 6u , i.e 20% increasse from 5u

This year the girls= 12u , i.e. twice of boys this year.

Girls this year is 80% of girls last year

80% => 12u

100% => 12u/0.8 = 15u <-last year girls

5u + 15u = 1760

20u =1760

u = 88

a) Last year boys = 5u = 5(88) = 440#

b) Total participants for last year = 20u

Total paticipants for this year = 6u+12u = 18u

Reduce by 2u

% reduction = 2u/20u X 100 = 10% ###

We can also select boys to be 10u at first if you want,, which will also work well with a 20% increase.

e.g Let last year boys be 10u,

This year boys will be 12u, i.e 20% increase,

This year girls will be 24u , i.e. twice of this year boys

80% =>24u

100%=> 24u/0.8 = 30u Last year girls

30u+10u = 1760

40u=1760

u = 44

a) 10u = 440 #

b) reduction by 40u - 36u = 4u

% reduction = 4u/40u X 100 = 10% ###