Tutor MathsGuru: Ask me for your burning Maths questions!

[kancheongmum]

Hifive:

Hi everyone


Need help with this question:
Source : Catholic High Sch P5 SA2 2009

http://postimage.org/image/2pa7ck5xg/

Thanks in advance.

Hi Hifive

area of triangles whose bases are on the length of rectangle:

1/2 x 6 x 12 = 36 m2

area of triangles whose bases are on the breath of rectangle:

1/2 x 2 x 24 = 24 m2

total shaded area 36 + 24 = 60 m2

[Dharma]

CJM:

At a party, 3/7 of the people attending were adults. 2/5 of the children were boys. If there were 48 girls,


a) how many children were there ?
b) how many people were ast the party ?

Adults => 3/7
Children => 4/7
Boys => 2/5 x 4/7 = 8/35
Girls =>3/5 x 4/7 = 12/35

12u = 48
1u = 4

Number of children = 20u = 20 x 4 = 80

Number of people = 35u = 35 x 4 = 140

[Dharma]

CJM:

A kettle has 420ml more water than a jug. When 150ml of water is poured from the jug into the kettle, thre are 4 times as much water in the kettle as the jug. How much water is there in the jug now ?

1u – 1p = 420 ------------- ( 1 )

Jug : 1p – 150
Kettle = 1u + 150

4p – 600 = 1u + 150
4p – 1u = 750 ------------ ( 2 )
( 1 ) + ( 2 )

3p = 1170
1p = 390
Amount of water in jug now = 1p – 150 = 390 – 150 = 240

Amount of water in jug now is 240 ml

[Dharma]

ABCDE:

Vanilla Cake:

[quote=\"beauty queen\"]Mr Samad made some toys to sell. He sold 20% of the toys on Monday. He sold 27 toys on Tuesday. On Wednesday he sold 10% of the remaining toys. After that he found out that the toys he had left was 1 more than 1/2 the number of toys he had made. How many toys did he make.

The number of toys made by Mr Samad was 115. But on working backwards, the number of toys sold on Wednesday is in decimals! Will leave this question for others to solve.

Thks.

In case u need the wrking :

Y x 80% = 0.8Y
(0.8y - 27) X 90% = 0.72Y - 24.3
0.72 Y - 24.3 = 0.5Y + 1
0.72Y = 0.5Y + 25.3
0.22Y ----- 25.3
Y = 115
They hvnot asked on WEdnesday.so, leave it.But as VC mentioned, it'll b in decimals.[/quote]Monday
Sold : 20% x 100u = 80u
Left : 80u

Tuesday
Sold : 27
Left : 80u – 27

Wednesday
Sold : 10% x (80u – 27 ) = 8u – 2.7
Left : 90% x (80u – 27) = 72u – 24.3

72u – 24.3 = 50u + 1
22u = 25.3
1u = 1.15

Check the number toys sold on Wednesday = 8u – 2.7 = 6.5 (Impossible!!!)

How could Mr Samad ever sell 6.5 toys ???? There is a flaw in the question and if it happens in PSLE, it is likely that all students will be given full marks for this question. (JMO)

[Yu Xuan]

Herbie:

Hi dharma, i hv one qn,

16 girls and some boys raised a total of $2600 for their sch pocket money fund. Each boy raised $40 more than each girl. If there were 2 more girls than boys, how much more money did the boys raise than the girls?

$ related qn is a problemarea for my Ds. Do u hv any advise on how to conquer $ n quantity qn? Many tx

Hi Herbie & Dharma, may I offer my 2 cents worth...

Boys --> 16 - 2 =14

Remove the extra $40 raised by each boy from the total amt raised, so that each boy and girl raise the same amt;
$2600 - ($40 * 14) = $2040

$2040 / (16 + 14) = $68 (amt raised by each girl)
$68 + $40 = $108 (amt raised by each boy)

Diff;
( $108 * 14 ) - ( $68 * 16 ) = $424

[CJM]

Dharma:

CJM:

A kettle has 420ml more water than a jug. When 150ml of water is poured from the jug into the kettle, thre are 4 times as much water in the kettle as the jug. How much water is there in the jug now ?

1u – 1p = 420 ------------- ( 1 )

Jug : 1p – 150
Kettle = 1u + 150

4p – 600 = 1u + 150
4p – 1u = 750 ------------ ( 2 )
( 1 ) + ( 2 )

3p = 1170
1p = 390
Amount of water in jug now = 1p – 150 = 390 – 150 = 240

Amount of water in jug now is 240 ml

Hi Dharma,

How to relate 1u & 1p ?
Need to draw model for this ?

[CJM]

Dharma:

CJM:

At a party, 3/7 of the people attending were adults. 2/5 of the children were boys. If there were 48 girls,


a) how many children were there ?
b) how many people were ast the party ?

Adults => 3/7
Children => 4/7
Boys => 2/5 x 4/7 = 8/35
Girls =>3/5 x 4/7 = 12/35

12u = 48
1u = 4

Number of children = 20u = 20 x 4 = 80

Number of people = 35u = 35 x 4 = 140

thank u : )

[CJM]

biniv300:

CJM:

At a party, 3/7 of the people attending were adults. 2/5 of the children were boys. If there were 48 girls,


a) how many children were there ?
b) how many people were ast the party ?

ans
(a)64
(b)112

hi biniv300,

the answer is
80 and 140.

[Vanilla Cake]

CJM:

Dharma:

[quote=\"CJM\"]A kettle has 420ml more water than a jug. When 150ml of water is poured from the jug into the kettle, thre are 4 times as much water in the kettle as the jug. How much water is there in the jug now ?

1u – 1p = 420 ------------- ( 1 )

Jug : 1p – 150
Kettle = 1u + 150

4p – 600 = 1u + 150
4p – 1u = 750 ------------ ( 2 )
( 1 ) + ( 2 )

3p = 1170
1p = 390
Amount of water in jug now = 1p – 150 = 390 – 150 = 240

Amount of water in jug now is 240 ml

Hi Dharma,

How to relate 1u & 1p ?
Need to draw model for this ?[/quote]Hi CJM,
Is this P4 Maths? While waiting for Uncle Dharma's reply, here's my suggested model solution for your review:

In the end
K: [][150][420][150]
J: [][150]

[150] must be in dotted form. I use red colour to represent it in dotted form.

4 times as much water in the kettle as the jug means 4 times of J=K.
4 units of J = 1 unit of K
4[]=[]+150+420+150
3[]=720
[]=240

1 unit of [] of J =240 ml ie Amount of water in the jug now = 240 ml

Hope this helps.

[iFruit]

Let Distance walked by Toby = d, and his speed = s, time taken = d/s


Then distance walked by Samad = d + 20 and his speed = s +4

d/s = (d+20)/(s+4)---> (d+20)/d = (s+4)/s---> 1+20/d = 1+4/s

so 20/d = 4/s ---> d/s = 5 hours.

So Toby and Samad walked for 5 hours before they met.

Samad walked 10km in 1 hour (5-4), or his speed is 10km/h

beauty queen:

One more question mathgurus

i think an easy one?

Samad and Toby walked from Town A to Town B at the same time. Samad was faster than Toby by 4km/h. When Samad reached Town B in 4 hours, he immediately walked back to Town A. On the way back he met toby who was 10 km away from Town B. What was Samad's speed