Q&A - P5 Math

[speedmaths.com]

Hi all,
I have 2 questions to ask.


THANK ALL..

I think the answer should be 210 boys.

You can explain using model or algebra.

Let me do it in model.

Let the number of girls be 10 x ,
then the number of boys will be 10 x + [90]

After 80% boys and 30% girls left, we have remaining

girls: 7 x
boys: 2 x + 18 Note: 90/10 x 2 = 18

Now girls is double of boys, i.e.
7 x = 2 x + 18 + 2 x + 18
so
3 x = 36
= 12

Number of boys at first = 10 x 12 + 90 = 210 (Ans)

Hi,

Yes, answer sh be 210.
(Not 420)

Cheers



speedmaths
.

[Daddy]

Thanks all for the answers.

Q18 answer is 210.

Thank again..

[Daddy]

Hi,

"triangle BPC is 1/4 of the rectangle. (because P is the midpoint of the width)
so the rectangle's area is 24 x 4 = 96"

How did you know BPC is 1/4 of the rectangle?
Why "the rectangle's area is 24 x 4 = 96"? But the picture have one 16cm2 below and a big triangle on top.

[Daddy]

Hi,

Not so understand for
"boys: 2 x + 18 Note: 90/10 x 2 = 18"

Thank.

[Kangkangteo]

Hi all,
I have 2 questions to ask.


THANK ALL..

DP = PC, so
Area APD = Area BPC = 24 sq cm

Area ABCD = 2 x (Area APD + Area BPC)
= 2 x (24 + 24)
= 96 sq cm

AQ = 1/3 QD, so QD = 3/4 AD
Area QPD = 3/4 Area APD
= 3/4 x 24
= 18 sq cm

96 - 24 - 16 - 18 = 38 sq cm

Area of quadrilateral ABPQ is 38 sq cm

[Kangkangteo]

Hi all,
I have 2 questions to ask.


THANK ALL..

G : 100u
B : 100u + 90

20% x (100u + 90)= 20u + 18

70% x 100u = 70u

70u ---> 2 x (20u + 18)

30u --> 36

100u ---> 36/30 x 100 = 120

120 + 90 = 210 boys

There were 210 boys at the fun fair at first.

[alfretztay]

Hi,

"triangle BPC is 1/4 of the rectangle. (because P is the midpoint of the width)
so the rectangle's area is 24 x 4 = 96"

How did you know BPC is 1/4 of the rectangle?
Why "the rectangle's area is 24 x 4 = 96"? But the picture have one 16cm2 below and a big triangle on top.

I hope the following steps will help :-

1.Draw a horizontal and a vertical line through P; and another line joining A and P.
2. One should be able to see four equal triangles above P and another four below it.
3. Hence, "triangle BPC is 1/4 of the rectangle" ABCD.

[alfretztay]

Hi,

Not so understand for
"boys: 2 x + 18 Note: 90/10 x 2 = 18"

Thank.

As "the number of boys will be 10 x + [90]", after 80% boys left, we would have 20% of (10u + 90) = 2u + 18. Hence, "boys: 2 x + 18 Note: 90/10 x 2 = 18."

[Bunny27]

Hi,
Can someone help me on this problem sum?
1. At first, Maria had $243 and Huimei had $183. Later, eachof them bought a calculator and a dictionary. The dictionary cost twice as much as the calculator. Then the ratio of Maria's money to Huimei's money became 3:2.
a) How much money did Maria have left?
b) What was the cost of each dictionary?

Thank you...

[Bunny27]

Hi,

Not so understand for
"boys: 2 x + 18 Note: 90/10 x 2 = 18"

Thank.

As "the number of boys will be 10 x + [90]", after 80% boys left, we would have 20% of (10u + 90) = 2u + 18. Hence, "boys: 2 x + 18 Note: 90/10 x 2 = 18."

Bunny27

 Post subject: P5 Ratio

Posted: 27 Jul 2014 21:03 

OrangeBelt
Joined: 26 Jan 2011 21:18
Posts: 69 

Hi,
Can someone help me on this problem sum?
1. At first, Maria had $243 and Huimei had $183. Later, eachof them bought a calculator and a dictionary. The dictionary cost twice as much as the calculator. Then the ratio of Maria's money to Huimei's money became 3:2.
a) How much money did Maria have left?
b) What was the cost of each dictionary?

Thank you...