Tutor MathsGuru: Ask me for your burning Maths questions!

[Vanilla Cake]

liketoeat:

The average mass of 5 blocks is 1.58 kg. When some identical cubes with a mass of 1.6 kg each were added to them, the average mass became 1.595 kg. How many cubes were added?

Since this is a P6 question then use algebra which is good enough to solve and gain full marks.
Let number of cubes added be n
( 5x1.58 )+( nx1.6 )=( n+5 )x1.595
n=15
Number of cubes added = 15

Hope other members will forward with non-algebraic approach so that readers of this forum can learn.

[Dharma]

Vanilla Cake:

liketoeat:

The average mass of 5 blocks is 1.58 kg. When some identical cubes with a mass of 1.6 kg each were added to them, the average mass became 1.595 kg. How many cubes were added?

Since this is a P6 question then use algebra which is good enough to solve and gain full marks.
Let number of cubes added be n
( 5x1.58 )+( nx1.6 )=( n+5 )x1.595
n=15
Number of cubes added = 15

Hope other members will forward with non-algebraic approach so that readers of this forum can learn.

http://www.postimage.org/image.php?v=aVb175J

[Vanilla Cake]

Dharma:

Vanilla Cake:

[quote=\"liketoeat\"]The average mass of 5 blocks is 1.58 kg. When some identical cubes with a mass of 1.6 kg each were added to them, the average mass became 1.595 kg. How many cubes were added?

Since this is a P6 question then use algebra which is good enough to solve and gain full marks.
Let number of cubes added be n
( 5x1.58 )+( nx1.6 )=( n+5 )x1.595
n=15
Number of cubes added = 15

Hope other members will forward with non-algebraic approach so that readers of this forum can learn.

http://www.postimage.org/image.php?v=aVb175J[/quote]Thanks, Dharma for your wonderful visual solution.
This is what is known as 抛砖引玉 - 比喻说出自己粗浅的意见引出别人高明的见解.

[Tang]

Dharma:

Vanilla Cake:

[quote=\"liketoeat\"]The average mass of 5 blocks is 1.58 kg. When some identical cubes with a mass of 1.6 kg each were added to them, the average mass became 1.595 kg. How many cubes were added?

Since this is a P6 question then use algebra which is good enough to solve and gain full marks.
Let number of cubes added be n
( 5x1.58 )+( nx1.6 )=( n+5 )x1.595
n=15
Number of cubes added = 15

Hope other members will forward with non-algebraic approach so that readers of this forum can learn.

http://www.postimage.org/image.php?v=aVb175J[/quote]Increase in average --> 1.595 - 1.58 = 0.015

Total increase --> 0.015 x 5 = 0.075 kg

Decrease in average --> 1.600 - 1.595 = 0.005

So number of cubes added --> 0.075/0.005 = 15 cubes

15 cubes were added.

[Almighty]

ruyu:

Vanilla Cake:

[quote=\"YLH88\"]6) Mark can climb uphill at an average speed of 2km/h and go downhill at an average speed of 6km/h. Going first uphill and then downhill, without stopping and using the same route, what will his average speed be for the entire trip ?

Assume the distance of the route be unit.
Total time taken = unit/2 + unit/6 = 4units/6 = 2units/3
Distance = unit
Average speed = unit÷2 units/3 = unitx3/2units = 3/2 = 1.5 km/h

This is similar to NMOS 2009 Prelim round Q3. Where is this question taken from?

dont understand :? care to explain?[/quote]HI Vanilla cake,
He is asking for the entire trip. So, shouldn't it be 1.5 X 2 = 3km/h?
12kmX2 = 24Km
12/2 = 6hr
12/6 = 2hr
6+2 = 8 hr
8hr ------24km
1hr -------? (3km)

Pl.clarify

[firebird]

Dear Vanilla cake and Tang


Good afternoon.

Thank you very much for your solution.

Vanilla cake, very sorry for the incorrect question and troubling you a lot.

With best regards
firebird

[Almighty]

Almighty:

Hi Friends,


Water was poured into an empty rectangular Tank X until it reached a height of 20cm. Some of the water was then poured into Tank Y which contained 1.5 litres of water until the height of the water in both the tanks were the same.Find the new height of the water in Tank Y.

MY working is :
Volume / base area = Height
So for Tank Y, Base area = 1000 cm 2
1500 / 1000 = 1.5 cm

Height of water in Tank X - Height in Tank Y = 20 - 1.5 = 18.5cm
So, to make it same, 18.5 / 2 = 9.25cm
Therefore new Height of Tank Y = 9.25 + 1.5 = 10.75 cm

Can anyone pointout y i cannot do like this? The method followed in the assessment book is different hence the answer is also different which is 12.6cm.

Will write below the method followed by the book is:
Volume in Tank X: 50x30x20 = 30000cm3
Totla volume = 30000+ 1500 = 31500 cm3
50X30Xh+40X25h ----------- 31 500
1500 h +1000h ---- 31 500
h --- 31500/2500 = 12.6 cm
Now can anyone say where i went wrong?

[YLH88]

Hi all,


for the below question which was asked previously in this forum,
why do we take 1u = $725, then 5u = $725 x 5 = $3625, and yet $5125 - $3265 = $1500 ? How do we get 5 sets ?

http://www.postimage.org/image.php?v=TsP8l5A

Thank you very much!

[Vanilla Cake]

YLH88:

Hi all,


for the below question which was asked previously in this forum,
why do we take 1u = $725, then 5u = $725 x 5 = $3625, and yet $5125 - $3265 = $1500 ? How do we get 5 sets ?

http://www.postimage.org/image.php?v=TsP8l5A

Thank you very much!

Alternative solutions while waiting for Mathsguru's reply:

Total spent on bags and wallets= $5850
Money spent on bags was $4400 more than money spent on wallets.
$(5850-4400)÷2=$725

B: [$725][$4400]
W:[$725]

Ann bought 5 times as many bags as wallets.

Cost of 1 unit of bag
5 units of bags x cost of 1 bag = $5125
1 unit of bag x cost of 1 bag = $1025

Cost of 1 unit of wallet
1 unit of wallet x cost of 1 wallet = $725

Value of 1 unit
Cost of 1 bag is $60 more than 1 wallet
Difference in 1 unit of bags and 1 unit of wallets = $1025-$725=$300
Difference of $300 is due to difference of $60
1 unit = $300/$60 = 5

Cost of 1 wallet
1 unit of wallet x cost of 1 wallet = $725
1 x 5 x cost of 1 wallet = $725
Cost of 1 wallet = $725÷5 = $145

OR

Number of units-quantity
Bag: 5u
Wallet: u

Value-unit cost
Bag: v+60
Wallet: v

Total amount =Number x Value
Bag: 5uv+300u
Wallet: uv

Wallet-total amount
uv = 725
5uv=3625

Bag-total amount
5uv+300u=5125
Since 5uv=3625, so 3625+300u=5125
300u=5125-3625
300u = 1500
u = 5

1 unit of wallet x cost of 1 wallet = $725
1 x 5 x cost of 1 wallet = $725
Cost of 1 wallet = $725÷5 = $145

OR

$5850-$4400=$1450
$1450÷2=$725 ->Total cost of wallets
$725+$4400=$5125-> Total cost of bags

Cost of 5 units of bags = $5125
Cost of 1 unit of bag = $5125÷5=$1025
Cost of 1 unit of wallet = $725

Difference in cost of 1 unit of bag and 1 unit of wallet =$1025-$725=$300
Difference in cost per each of bag against each of wallet = $60
Number of wallets = 300÷60=5
Cost of 1 wallet = $725÷5 = $145

[Maths Monster]

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