## Q&A - PSLE Math

### Re: Q&A - PSLE Math

Rate of spending per day.

1St scenerio

M:V

10:15

2nd scenerio

M:V

15:24

Since V spent all his money in both scenerio, we can say that the Ratio in both scenerio must be the same.

New Ratio.

1St scenerio

M:V

10x24: 15x 24

240:360

2nd scenerio

M:V

15x15:24:15

225:360

240U + 60(What M has left in 1st scenerio) = 225U + 80( What M has left in 2nd scenerio)

15U=20

1U = 1.3333333333333333

1.33333333333333 x 360 = 480 (a)

1.33333333333333 x 240 + 60 = 380 (b)

Solved by DS.

1St scenerio

M:V

10:15

2nd scenerio

M:V

15:24

Since V spent all his money in both scenerio, we can say that the Ratio in both scenerio must be the same.

New Ratio.

1St scenerio

M:V

10x24: 15x 24

240:360

2nd scenerio

M:V

15x15:24:15

225:360

240U + 60(What M has left in 1st scenerio) = 225U + 80( What M has left in 2nd scenerio)

15U=20

1U = 1.3333333333333333

1.33333333333333 x 360 = 480 (a)

1.33333333333333 x 240 + 60 = 380 (b)

Solved by DS.

### Re: Q&A - PSLE Math

Solved by DS

First Scenario:

At First

M : V Total

60 + 10u : 15u 25u + 60

Change

-10u : -15u

At End

60 : 0

Second scenario :

At First,

M : V

15p + 80 : 24p 39p + 80

Change,

-15p : -24p

At End,

80 : 0

Since the amount for V in 2 scenario's are same, 15u = 24p, 3u = 8p

Total will be the same.

25u + 60 = 39p + 80

Make them as same units,

25u + 60 = 40p + 60

substitute 25u + 60 with 40p + 60,

equation is 40p + 60 = 39p + 80

p = 20

V -> 24p

24p = 480 (a)

M -> 15p + 80

15p = 300

M -> 300 + 80 = 380 (b)

First Scenario:

At First

M : V Total

60 + 10u : 15u 25u + 60

Change

-10u : -15u

At End

60 : 0

Second scenario :

At First,

M : V

15p + 80 : 24p 39p + 80

Change,

-15p : -24p

At End,

80 : 0

Since the amount for V in 2 scenario's are same, 15u = 24p, 3u = 8p

Total will be the same.

25u + 60 = 39p + 80

Make them as same units,

25u + 60 = 40p + 60

substitute 25u + 60 with 40p + 60,

equation is 40p + 60 = 39p + 80

p = 20

V -> 24p

24p = 480 (a)

M -> 15p + 80

15p = 300

M -> 300 + 80 = 380 (b)

- acehkr3009
- OrangeBelt
**Posts:**42**Joined:**Tue Mar 24,

### Re: Q&A - PSLE Math

Hi Please advise on this question:

Machine A and Machine B working together take 7 days to finish producing 100 boxes of toys.

Mr Lee switched on Machine A and Machine B for 4 days, followed by Machine A alone for 7 days. Then he needed to switch on Machine B alone for 1 more day to complete producing the same 100 boxes of toys.

How long will Machine A alone take to produce the 100 boxes of toys?

Thanks in advance.

Machine A and Machine B working together take 7 days to finish producing 100 boxes of toys.

Mr Lee switched on Machine A and Machine B for 4 days, followed by Machine A alone for 7 days. Then he needed to switch on Machine B alone for 1 more day to complete producing the same 100 boxes of toys.

How long will Machine A alone take to produce the 100 boxes of toys?

Thanks in advance.

### Re: Q&A - PSLE Math

Hi

Could anyone help me on Speed topic question:thanks

Mr Koh & Mr Ng left the shopping mall at the same time, travelling in opposite direction along a straight road.Mr Koh drove at a speed 80 km/h while Mr Ng drove at a speed of 70 km/h.After how long will they be 30 km apart?

Could anyone help me on Speed topic question:thanks

Mr Koh & Mr Ng left the shopping mall at the same time, travelling in opposite direction along a straight road.Mr Koh drove at a speed 80 km/h while Mr Ng drove at a speed of 70 km/h.After how long will they be 30 km apart?

### Re: Q&A - PSLE Math

Pls help

A farmer had some geese and ducks.

If he bought another 40 ducks, the ratio of the number of ducks to the number of geese would become 5:6.

If he bought another 60 geese instead, then the ratio of the number of ducks to the number of geese would become 2:3.

How many more geese than ducks did the farmer have?

A farmer had some geese and ducks.

If he bought another 40 ducks, the ratio of the number of ducks to the number of geese would become 5:6.

If he bought another 60 geese instead, then the ratio of the number of ducks to the number of geese would become 2:3.

How many more geese than ducks did the farmer have?

### Re: Q&A - PSLE Math

wiser2020 wrote:Hi

Could anyone help me on Speed topic question:thanks

Mr Koh & Mr Ng left the shopping mall at the same time, travelling in opposite direction along a straight road.Mr Koh drove at a speed 80 km/h while Mr Ng drove at a speed of 70 km/h.After how long will they be 30 km apart?

So you have a shopping point. which in fact is the starting point. Lets call this point M. Now, Mr Koh left the shopping mall at a constant speed of 80km/h, while Mr Ng left at the opposite direction at a speed of 70km/h.

Let Mr Koh be K and Mr Ng be N

K < M > N

We can assume that K travels to the left and N travels to the right. Now, we know that after one hour, K will be 80 km left of M, and N will be 70km right of M. So after one hour, K and N will be 100km apart. Now after 2 hours, K will be 160km left of M and N will be 140km right of M. Realise, every hour, their distance apart increases by 150km? We can safely say that the distance apart increases by (80+70)km/h = 150km/h.

So,

Distance = Speed x Time

30km = 150km/h x Time

Time = 30km / 150km/h = 1/5h = 12min

### Re: Q&A - PSLE Math

Let the number of ducks be d and the number of geese be g,am.virdi wrote:Pls help

A farmer had some geese and ducks.

If he bought another 40 ducks, the ratio of the number of ducks to the number of geese would become 5:6.

If he bought another 60 geese instead, then the ratio of the number of ducks to the number of geese would become 2:3.

How many more geese than ducks did the farmer have?

d + 40 = 5/6 x g (Equation 1)

g + 60 = 3/2 x d (Equation 2)

From Equation 1,

d + 40 = 5/6 x g

d + 40 - 40 = 5/6 x g - 40

d = 5/6 x g - 40

Substitute d = 5/6 x g - 40 into Equation 2,

g + 60 = 3/2 x (5/6 x g - 40)

g + 60 = 3/2 x 5/6 x g - 3/2 x 40

g + 60 = 15/12 x g - 60

g + 60 + 60 = 15/12 x g - 60 + 60

g + 120 = 15/12 x g

g + 120 - g = 15/12 x g - g

120 = 3/12 x g

g = 120 / (3/12)

g = 120 x 12/3

g = 120 x 4

g = 480

Substitute g = 480 into d = 5/6 x g - 40

d = 5/6 x 480 - 40

d = 400 - 40

d = 360

g - d = 120

There is 120 more goose than duck.

### Re: Q&A - PSLE Math

An easier way solved by DS

6u + 60 =3p

5u-40=2p

4u+40 =2p

5u-40=4U+40

1U = 80

80X 6 = 480 [goose]

4x80+40 =360 [Duck ]

480-360 =

6u + 60 =3p

5u-40=2p

4u+40 =2p

5u-40=4U+40

1U = 80

80X 6 = 480 [goose]

4x80+40 =360 [Duck ]

480-360 =

**120**### Re: Q&A - PSLE Math

hoddle wrote:Hi

Need help on the below.

28x18x15x4/5=6048

Find the base area.

Base area of A: base area of B

28x18 : 168

504 : 168

1.5 times x 168 = 252

6048/(252+504)= 8

8 x 252 = 2016 cm3

Solved by DS.

Last edited by NerdyMath on Fri Sep 25, 2015 11:47 am, edited 1 time in total.