Q&A - PSLE Math

[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.

[corneyAmber]

Daddy:

Thanks MathIzzzFun & ivanhoo99.


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

litres convert to cubic cm.
1 litre = 1000 cubic cm.

So 48.4 l = 48400 cubic cm or cm3

Reason = litres measure volume and to get volume from cm, it has to be cubic cm or cm3.....that will be easy for the children to remember. cm2 only give areas.

[MathIzzzFun]

Daddy:

Thanks MathIzzzFun & ivanhoo99.


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

Hi

for volume, it is cm3 or cubic cm, 1000 cubic cm (cm3) = 1l = 1000 ml
for area, it is cm2 square cm.

cheers.

[stary]

Hi all,

Have a problem here…

A pail contains some pebbles and water. The total volume of the pebbles and water in the pail is 2300 cm3. A cube-shaped tank containing some water has a base area of 361 cm2. The ratio of the volume of water in the tank to the total volume of pebbles and water in the pail is 3:5. What is the water level in the tank? Give your answer in cm, correct to 2 decimal places.
(a) Find the increase in water level of the tank in cm.
(b) A stick is 13cm long. If the stick just touches the water surface in the cube-shaped tank vertically, find the length of the stick that is exposed outside the tank.

[Daddy]

Thanks MathIzzzFun.


Have another math question to ask.

Joey had 5 time as much money as her brother, John. After her father gave her $59 and gave John $49. Joey now had twice as much as John. How much did Joey have at first.

Thank
Daddy

[corneyAmber]

stary:

Hi all,

Have a problem here...

A pail contains some pebbles and water. The total volume of the pebbles and water in the pail is 2300 cm3. A cube-shaped tank containing some water has a base area of 361 cm2. The ratio of the volume of water in the tank to the total volume of pebbles and water in the pail is 3:5. What is the water level in the tank? Give your answer in cm, correct to 2 decimal places.
(a) Find the increase in water level of the tank in cm.
(b) A stick is 13cm long. If the stick just touches the water surface in the cube-shaped tank vertically, find the length of the stick that is exposed outside the tank.

Vol of water in tank : vol of pebbles and water = 3 : 5
3: 5 = V : 2300
V = 3/5 x 2300 = 1380
Base area of tank = 361
Hence water level = 1380/361 = 3.82cm

Is there missing information? Something must happen to cause an increase in the water level to solve (a), eg, the pail's water and pebbles poured into the cube??

[stary]

Daddy:

Thanks MathIzzzFun.


Have another math question to ask.

Joey had 5 time as much money as her brother, John. After her father gave her $59 and gave John $49. Joey now had twice as much as John. How much did Joey have at first.

Thank
Daddy

Hi,

Joey : John
5 units : 1 unit
+$59 +$49
2 parts : 1 part

2 units + $98 = 5 units + $59
3 units -> $98-$59 = $39
5 units -> 5/3 x $39 = $65

Cheers!

[stary]

ksi:

stary:

Hi all,

Have a problem here...

A pail contains some pebbles and water. The total volume of the pebbles and water in the pail is 2300 cm3. A cube-shaped tank containing some water has a base area of 361 cm2. The ratio of the volume of water in the tank to the total volume of pebbles and water in the pail is 3:5. What is the water level in the tank? Give your answer in cm, correct to 2 decimal places.

When all the pebbles are transferred fro the pail to the cube-shaped tank, the total volume of water and pebbles in the tank becomes 2282.5 cm3.

(a) Find the increase in water level of the tank in cm.
(b) A stick is 13cm long. If the stick just touches the water surface in the cube-shaped tank vertically, find the length of the stick that is exposed outside the tank.

Vol of water in tank : vol of pebbles and water = 3 : 5
3: 5 = V : 2300
V = 3/5 x 2300 = 1380
Base area of tank = 361
Hence water level = 1380/361 = 3.82cm

Is there missing information? Something must happen to cause an increase in the water level to solve (a), eg, the pail's water and pebbles poured into the cube??

Hi ksi, i've added the missing info...

[corneyAmber]

stary:

ksi:

[quote=\"stary\"]Hi all,

Have a problem here...

A pail contains some pebbles and water. The total volume of the pebbles and water in the pail is 2300 cm3. A cube-shaped tank containing some water has a base area of 361 cm2. The ratio of the volume of water in the tank to the total volume of pebbles and water in the pail is 3:5. What is the water level in the tank? Give your answer in cm, correct to 2 decimal places.

When all the pebbles are transferred fro the pail to the cube-shaped tank, the total volume of water and pebbles in the tank becomes 2282.5 cm3.

(a) Find the increase in water level of the tank in cm.
(b) A stick is 13cm long. If the stick just touches the water surface in the cube-shaped tank vertically, find the length of the stick that is exposed outside the tank.

Vol of water in tank : vol of pebbles and water = 3 : 5
3: 5 = V : 2300
V = 3/5 x 2300 = 1380
Base area of tank = 361
Hence water level = 1380/361 = 3.82cm

Is there missing information? Something must happen to cause an increase in the water level to solve (a), eg, the pail's water and pebbles poured into the cube??

Hi ksi, i've added the missing info... [/quote](a) When pebbles are added in , the volume of the pebbles will be the volume of water raised in the tank.
Volume of pebbles = 2282.5-1380 = 902.5
So level of water increase = 902.5/361 = 2.5cm

(b) Height of the tank = Sq root of 361 = 19 (because it is a cubic tank)
So if water is at 2.5+3.82= 6.32cm
19-6.32 = 12.68cm
So the length of stick exposed outside the tank would be 13-12.68=0.32cm.