Tutor MathsGuru: Ask me for your burning Maths questions!

[corneyAmber]

ganchiong:

ksi:

[quote=\"ganchiong\"]Need help in the following question:


Jeffrey wants to pack some identical cuboids into a container. What is the maximum number of cuboids Jeffrey can pack into the container?

Dimension for cuboid:2cmx2cmx3cm and container: 6cmx11cmx14cm

TIA

is the answer 77?

yes[/quote]container = 6x11x14 = 924
cuboid = 2x2x3 = 12
max. Number of cuboids = 924/12 = 77

[kancheongmum]

ksi:

ganchiong:

[quote=\"ksi\"]
is the answer 77?

yes

container = 6x11x14 = 924
cuboid = 2x2x3 = 12
max. Number of cuboids = 924/12 = 77[/quote]Hi ksi and ganchiong
I don't think the answer is 77. You cannot divide the volume of the container by the volume of the cuboid. You have to approach this type of question this way. Minimize the remainder. Divide each dimension by each dimension. Try not to have remainder.

6/3 -- 2 cuboids
11/2 -- 5 cuboids remain 1 cm
14/2 -- 7 cuboids

Max no. 2 x 5 x 7 = 70 cuboids

[snowman.022851697]

Yes kancheongmum is right. You can’t squeeze a 2-cm cube into a 1-cm space. Reason being simple: solids can’t be compressed…


If you use a calculator and end up with decimal, round down, not up, to the nearest whole number

[Herbie]

Hi I have one qn


Candle A and Candle B are of the same length. Candle A which is broader can burn for 5 hours while Candle B the thinner candle can burn for 4 hour, If both candles are lighted at the same time, how long does it take for Candle A to be twice as long left as Candle B?

Kindly advise.

Tx

[Vanilla Cake]

Herbie:

Candle A and Candle B are of the same length. Candle A which is broader can burn for 5 hours while Candle B the thinner candle can burn for 4 hour, If both candles are lighted at the same time, how long does it take for Candle A to be twice as long left as Candle B?

This question is from River Valley Primary School 2010 P6 Prelim Paper 2 Q17 [5 marks].

Refer to http://psle2010a.blogspot.com/2010/09/rvps-p6-prelim-2010-p2-q17.html
A similar question solved by http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=280&postdays=0&postorder=asc&start=1530.

[Herbie]

Hi! Thanks Vc! I hv another qn. A fruitseller had some oranges, pears n durians. After selling some of them, there were 6 pears for every 5 oranges left and 7 oranges for every 3 durians left. He sold 168 oranges. He had 456 pears and oranges left. The no of pears sold was the Same as the no of durians sold. How many oranges had he at first? If the no of pears was twice the ö ofDurian at firSt, what the total no of pears and durians sold

[Daddy]

Hi ,


I have two questions to ask.

1) The total cost of 4 similar pouches and 7 similar lipsticks is $205. If 3 such pouches and 1 lipstick cost $90, find the cost of each pouch?


2) Alan and Jenny had an equal amount of money. Alan spent $20 each day and Jenny spent $36 each day. When Jenny had $40 left, Alan had five times as much money left as she. How much money did Alan have at first?

Thanks
Daddy

[Herbie]

Hi daddy

4p + 7L = 205
3p +1L= 90

12p + 21L = 615
12p + 4l = 360

21L -4L= 615-360
!7L=225
L=15
insert L=15 into the earlier eqn n you will get p= 25
each pouch = $25

[corneyAmber]

Daddy:

Hi ,


2) Alan and Jenny had an equal amount of money. Alan spent $20 each day and Jenny spent $36 each day. When Jenny had $40 left, Alan had five times as much money left as she. How much money did Alan have at first?

Thanks
Daddy

Money Jenny had at first = 40 + 36(# of days)
Money Alan had at first = (40x5) + 20(# of days)
40 + 36(# of days) = 200 + 20(# of days)
16(# of days) = 160
# of days = 10

Hence money Alan had at first = 200 + 20(10) = $400

[corneyAmber]

Daddy:

1) The total cost of 4 similar pouches and 7 similar lipsticks is $205. If 3 such pouches and 1 lipstick cost $90, find the cost of each pouch?

Thanks
Daddy

Alternative method:

3P + 1L = 90 => 1L = 90-3P
4P + 7L = 205
4P + 7(90-3P) = 205
4P - 21P = 205 -630
17P = 425
P = $25