8 July - Math

Dear all,
Sorry for the late post. I was very sickly on Sat and Sun - Fever, sore throat and runny nose. Still not feeling well- nose still runny.

For rate,  it is very easy. Look at Pg 123 of your WB, Q7

the rate of flow is 3 litres per minute. What does that mean?
 It means 1min -----  3 litres. So to find the time, you will need to find the volume first.

(7b)  volume -- (10 x 20 x 30) cubic cm = 6000 cubic cm
                                                                = 6 litres

 3 litres ------ 1 min
6 litres ------- 2 min.

Pg 131. You have two taps filling in the water, so find out in 1 min how much water is filled. How?

Tap A :  1 min ----- 3 litres
Tap B :  1 min ----- 2 litres

so for Tap A and Tap B : 1 min ---- (3 + 2 ) litres = 5 litres

Once you are clear of this, to find how time, what do you need? Yes, Volume of water.

Volume of water in the tank when it is half-filled
= (40 x 20 x 50 x 1/2 ) cubic cm
= (20 000) cubic cm
= 20 litres

5 litres ------- 1 min
20 litres ------ 4 min

Pg 132. Now you have one tap filling in water and the other draining out water, so how? Simple, apply the same concept.

Tap A : 1 min ---- 6 litres
Tap B : 1 min ---- 4 litres

Tap A and Tap B : 1 min ---- (6 - 4 ) litres = 2 litres

Once you get this relationship right, the rest will be mechanical.
So, what to find now?
Yes, the volume in the tank.

Volume = L x B x H
              = (20 x 10 x 30)
              = 6000 cubic cm
              = 6 litres

2 litres ------ 1 min
6 litres ------ 3 min.

See, rate in volume is SO easy right?

Please finish up your volume WB and complete your Revision 2 and also the practice paper that was given to you. For Practice Paper 1, make sure you go through the corrections on your own first.  Remember to log on to learnlogy for volume exercise.

We are left with 11 weeks.....  :(

Jia You!!!

Regards,
Mrs Mak