Q&A - PSLE Math

[raghupavithra]

thanks

[jieheng]

pensiveowl:

Hi.. Can someone pls help with this question - thanks!


Linda mixed 3 l of blue paint with 7 l of white paint. She then poured out 4 l of the mixture into a pail and added 6 l of red paint into the pail. Find the ratio of the volume of blue paint to the volume of red paint in the pail.

Volume of blue paint in 4 l of mixture = 3/(3+7) * 4 = 3/10 * 4 = 1.2

the ratio of the volume of blue paint to the volume of red paint in the pail = 1.2 : 6 = 12 : 60 = 1 : 5 (Ans)

[jieheng]

raghupavithra:

thanks

You are welcome .

Regards,

[pensiveowl]

Thanks jieheng

[eurostar]

wow the working solution for some so complicated

reaslly diff from our era

[S6169]

jieheng:

raghupavithra:

four boys, Alex,Ben,carl and dan shared the cost of a present equally. carl had some money but he did not have enough to pay for his share.Alex paid more to makeup the difference for carl. the amount of money paid by alex is 1/2of the total amount paid by ben, carl and dan. the amount of money paid by ben is 1/3 of the amount paid alex,carl,and dan. the amount of money paid by carl is 1/5 of the total amount paid by alex,ben and dan.if carl returned $38 to alex the next day, find the cost of the present.


how to solve this

the amount of money paid by carl is 1/5 of the total amount paid by alex,ben and dan
Carl paid []
total amount paid by Alex , Ben and Dan [][][][][]

Carl paid 1/6 of the total cost

Carl should pay 1/4 of the total cost as four boys shared the cost of a present equally

the amount that Alex paid more to makeup the difference for carl = 1/4 - 1/6 = 1/12

1u --> 38
12u --> 38*12 = 456

the cost of the present is $456 (Ans)

What is this part for? confuse the student? :roll:

[jieheng]

S6169:

jieheng:

[quote=\"raghupavithra\"]four boys, Alex,Ben,carl and dan shared the cost of a present equally. carl had some money but he did not have enough to pay for his share.Alex paid more to makeup the difference for carl. the amount of money paid by alex is 1/2of the total amount paid by ben, carl and dan. the amount of money paid by ben is 1/3 of the amount paid alex,carl,and dan. the amount of money paid by carl is 1/5 of the total amount paid by alex,ben and dan.if carl returned $38 to alex the next day, find the cost of the present.


how to solve this

the amount of money paid by carl is 1/5 of the total amount paid by alex,ben and dan
Carl paid []
total amount paid by Alex , Ben and Dan [][][][][]

Carl paid 1/6 of the total cost

Carl should pay 1/4 of the total cost as four boys shared the cost of a present equally

the amount that Alex paid more to makeup the difference for carl = 1/4 - 1/6 = 1/12

1u --> 38
12u --> 38*12 = 456

the cost of the present is $456 (Ans)

What is this part for? confuse the student? :roll:[/quote]the amount of money paid by ben is 1/3 of the amount paid alex,carl,and dan
Ben paid []
total amount paid by Alex , Carl and Dan [][][]

==> Ben paid 1/4 of the total cost (which is already mentioned in the question that four boys shared the cost of a present equally and only Carl did not have enough to pay for his share )

the amount of money paid by alex is 1/2of the total amount paid by ben, carl and dan
Alex paid []
total amount paid by Ben , Carl and Dan [][]

==> Alex paid 1/3 of the total cost

the amount that Alex paid extra for Carl = 1/3 - 1/4 = 1/12

which is the same as the amount that Alex paid more to makeup the difference for carl = 1/4 - 1/6 = 1/12

********************************************************

These steps are not require in order to solve this question .

If you do these steps , you will still get the same answer .

[jieheng]

pensiveowl:

Thanks jieheng

Hi pensiveowl ,

You are welcome.

Regards,

[pensiveowl]

I need help with this problem - can someone pls help solve it - thanks


http://www.positivelyquit.org/images/math.jpg\">

[jieheng]

pensiveowl:

I need help with this problem - can someone pls help solve it - thanks

http://i52.tinypic.com/2qxvo1k.jpg\">

Ratio of radius of large semi-circle to radius of medium semi-circle = 8 : 5
==> radius of large semi-circle / radius of medium semi-circle = 8/5
==> radius of large semi-circle = 8/5 * 15 = 24 cm

FG = GH = diameter of medium semi-circle = 2*15 = 30 cm

BC = AD = diameter of large semi-circle = 2*24 = 48 cm

BF = GC = (48-30)/2 = 9 cm

Area of medium semi-circle = 1/2*Pi*15*15 = 225/2*Pi

Area of large semi-circle = 1/2*Pi*24*24 = 288*Pi

Area of un-shaded BEF = Area of un-shaded CHG =Area of square ABFE - area of small quadrant = 9*9 - 1/4 *Pi*9*9 = 81- 81/4*Pi

Area of rectangle EFGH = 9*30 = 270

Area of shaded part
= Area of medium semi-circle + Area of large semi-circle - Area of un-shaded BEF - Area of un-shaded CHG - Area of rectangle EFGH
= 225/2 * Pi + 288*Pi - (81- 81/4*Pi)*2 - 270
= 225/2 * Pi + 288*Pi - 162 + 81/2 * Pi - 270
= 441*Pi - 432
= 953.44 square cm (Ans)