Q&A - P5 Math

[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

 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...

Let the cost of a calculator be 1u.
Then, $243-3u->3p and
$183-3u->2p.
1p->$60
3p->$180[answer for a)].
$183-3u->$120
3u->$63
1u->$21
2u->$24[answer for b)].

[Daddy]

Thank alfretztay.

[milo-cupcake]

Hi,
Need help with this question :

Kelvin had between $30 and $40 in $1 coins and 50-cent coins.

The ratio of the number of $1 coins to the number of 50-cent coins was 1:3. He exchanged some $1 coins for 50-cent coins. The ratio of the number of $1 to the number of 50-cent coins then became 1:5.

Find: a) the total number of money that Kelvin had.
b) the number of $1 coins which were exchanged for 50-cent coins.

Thks in advance!

[ILLUSDUCA]

Hi,
Need help with this question :

Kelvin had between $30 and $40 in $1 coins and 50-cent coins.

The ratio of the number of $1 coins to the number of 50-cent coins was 1:3. He exchanged some $1 coins for 50-cent coins. The ratio of the number of $1 to the number of 50-cent coins then became 1:5.

Find: a) the total number of money that Kelvin had.
b) the number of $1 coins which were exchanged for 50-cent coins.

Thks in advance!

Hello milo-cupcake,
Since $1 is equal to 2 x $0.5, we can change the ratio accordingly.
At first:
$1 : $0.5 ---> $(0.5 x 2) : $0.5
1 : 3 --------> 2 : 3, total = 5u

In the end,
$1 : $0.5 ---> $(0.5 x 2) : $0.5
1 : 5 --------> 2 : 5, total = 7u

Since the total amount of money in both ratio is the same, we can make their total in terms of units the same as well. To do so, we multiply them by 7 and 5 accordingly.

At first:
$(0.5 x 2) : $0.5 ----------------> $1 : $0.5
..........14 : 21, total = 35u -----> 7 : 21

In the end,
$(0.5 x 2) : $0.5 --------------> $1 : $0.5
..........10 : 25, total = 35u ----> 5 : 25

Given this ratio, the amount of money should be $1 x 7 coins + $0.5 x 21 coins = $17.5. OR $1 x 5 coins + $0.5 x 25 coins = $17.5

And since he had between $30 - $40, without spoiling our ratio's proportions, we can just multiply the ratio by 2. Then we will get:

At first:
$(0.5 x 2) : $0.5 ------------------> $1 : $0.5
..........28 : 42, total = 70coins--> 14 : 42

In the end,
$(0.5 x 2) : $0.5 ------------------> $1 : $0.5
..........20 : 50, total = 70coins--> 10 : 50

Total value now will be $1 x 14 coins + $0.5 x 42 coins = $35
a) Kelvin had $35.
b) comparing "at first and in the end", $1 exchanged = 14 coins minus 10 coins = 4 coins.

Hope this helps!

[alfretztay]

Thank alfretztay.

Glad to help; and you are most welcome.

[Daddy]

Hi kangkanteo

How you get

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

[Kangkangteo]

Hi kangkanteo

How you get

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

Given: AQ = 1/3 QD

If AQ --> 1u, QD ---> 3u

So AD = AQ + QD = 4u

Hence QD = 3/4 AD

Triangles QPD and APD have the same height.
Triangle QPD --- base QD while triangle APD --- base AD

[Daddy]

Thank Kangkangteo.

[Sruthi]

[IMG]http://i62.tinypic.com/e6xeth.jpg[/IMG] 7- please help with question : thanks in advance

[fohope]

Hi,
Could anyone help me on this problem? Thanks in advance.
From Nanyang CA 2013
The total values of 3 numbers A, B and C is 215. When the value of A is doubled, the value of B is decreased by 15 and the value of C is increased by 25, the values of the 3 numbers become the same. Find the value of A.