Q&A - PSLE Math

[MathIzzzFun]

is_me_lblue:

Hi, pls confirm my answer.


Figure. Number of oval
1. 1
2. 5
3. 13
4. 25
5. 41

Below answer for the Q is given in the answer sheet.
Q:how many ovals will there be in Figure 87 ?
A:14695 ( my answer is 705)


Q: which figure will have 5305 ovals ?
A: 5305(this is for sure wrong)

Hi is_me_lblue,

a) Number of ovals in fig 87
= 1 + (1+2+3+4+5+...+85+86) x 4
= 14965

b) Figure with 5305 ovals = Figure 52

Number of ovals in Figure n =
1+ (1+2+3+4+5+...+n-1) x 4 = 5305
(1+2+3+4+5+...+n-1) = 1326
n=52

cheers.

[Dharma]

Fig 1 => 1

Fig 2 => 5 = 4 + 1
Fig 3 => 13 = 9 + 4
Fig 4 => 25 = 16 + 9
Fig 5 => 41 = 25 + 16
Fig n => n^2 + (n - 1)^2

Fig 87 => 87^2 + 86^2 = 14965 ovals

If number of ovals is 5305

Take the average of n^2 and (n-1)^2 = 5305/2 = 2652.5
Square root of 2652.5 = 51.5

n is the next whole number > 51.5 (n = 52)

52^2 + 51^2 = 5305 (Fig. 52 has 5305 ovals)

[Hifive]

Hi


Need help with the following 2 questions:

http://www.flickr.com/photos/62186744@N04/5907323330/in/photostream/

http://www.flickr.com/photos/62186744@N04/5906768665/in/photostream/

Thanks in advance.

[MathIzzzFun]

Hifive:

Hi


Need help with the following 2 questions:

http://www.flickr.com/photos/62186744@N04/5907323330/in/photostream/

http://www.flickr.com/photos/62186744@N04/5906768665/in/photostream/

Thanks in advance.

Hi

Q2 ..


http://i54.tinypic.com/2q0lzyq.jpg\">

cheers.

[MathIzzzFun]

Hifive:

Hi


Need help with the following 2 questions:

http://www.flickr.com/photos/62186744@N04/5907323330/in/photostream/

http://www.flickr.com/photos/62186744@N04/5906768665/in/photostream/

Thanks in advance.

Hi

Q1..

http://i53.tinypic.com/anbgwg.jpg\">

cheers.

[Hifive]

Hi MathIzzzFun


Many thanks for your help with the 2 questions. Really appreciate.
Have a nice day.

[Daddy]

Hi,


Need help!! Thanks

An empty tank with a capacity of 48.4 litres. Water flows from TapA at 3.2 litres per min and from Tap B at 2.8 litres per min.
Tap A was turned on first. Tap B was turned on 2 min later. The taps were turned off at the same time when the tank was completely filled without overflowing. How much water flowed from Tap B?

Thanks

[ivanhoo99]

[quote]Hi,


Need help!! Thanks

An empty tank with a capacity of 48.4 litres. Water flows from TapA at 3.2 litres per min and from Tap B at 2.8 litres per min.
Tap A was turned on first. Tap B was turned on 2 min later. The taps were turned off at the same time when the tank was completely filled without overflowing. How much water flowed from Tap B?

Thanks[/quote]Capacity-48.4L=48400cm2

Tap A-3.2=3200cm2
Tap B-2.8=2800cm2

2minutes-A=3200*2=6400
3minutes-6400+3200+2800=12400
4minutes-12400+3200+2800=18400
.
.
.
9minutes-38800+3200+2800=48400cm2

B-(9-2)*2800=19600
19600cm2=19.6L

The answer is 19.6L
Hope this helps!

Good luck!

[MathIzzzFun]

Daddy:

Hi,


Need help!! Thanks

An empty tank with a capacity of 48.4 litres. Water flows from TapA at 3.2 litres per min and from Tap B at 2.8 litres per min.
Tap A was turned on first. Tap B was turned on 2 min later. The taps were turned off at the same time when the tank was completely filled without overflowing. How much water flowed from Tap B?

Thanks

Hi

After Tap A was turned on for 2 min, volume of water in tank = 2 x 3.2L= 6.4L

Remaining volume of tank to be filled = 48.4L - 6.4L = 42L

When both Tap A and Tap B were turned on, the total flow rate = 3.2L/min+2.8L/min = 6L / min

42L / 6L/min = 7 min
So, with both taps running, it would take another 7 min to fill the tank to the brim.

Amount of water from Tap B = 7min x 2.8L/min = 19.6L

cheers.

[Daddy]

Thanks MathIzzzFun & ivanhoo99.


Is 48.4L= 48400cm2 or 48400cm3. Convert litres to cm square or cm cube? which is which? Thanks.