Q&A - PSLE Math

[Vanilla Cake]

kavisuresh:

4. Given that p: (q+r)= 1:3, r: (q+s)=1:2, p:s = 2:5, a) find p:q:r:s b)find (r+q): (p+s)

Refer to http://4.bp.blogspot.com/_NGNaLTzN5_U/SrxCC0Mik4I/AAAAAAAAD0U/JUyLNBpK1lM/s1600-h/Maths0609SA2P2NYRatioQ12A.JPG and http://www.1800-teacher.com/images/fbfiles/images/P6_160910_Ratio.jpg.

kavisuresh:

8. Tracy counted the number of 10c coins, 20c coins and 50c coins in her piggy bank.The number of 10c coins was 24 more than the number of 50c coins. After spending 3/5 of the 10c coins, 1/4 of 20c coins and 18 50c coins,she had an equal number of 10c and 20c coins. The number of 50c coins now formed 40% of the remaining number of coins. a)How many 10c coins did Tracy have at first ?
b)How much did she spend in all ?

Refer to http://www.onsponge.com/index.php?option=com_kunena&Itemid=282&func=view&id=12598&catid=35#12598.

kavisuresh:

10. At carpark P, the number of lorries to that of vans was in the ratio 3:7. At carpark Q, the number of lorries to that of vans was in the ratio 8:9. When 40% more lorries from an industrial park entered carpark P and 20% of vans at carpark Q moved to carpark P, there were 76 fewer lorries at carpark P than at carpark Q. How many total vehicles were there altogether finally ?

Refer to http://www.onsponge.com/forum/35-thinkingmathonsponge/950-real-hard-ratio.html.

[Vanilla Cake]

kavisuresh:

1. The average mass of some parcels in a box was 20kg at first. When another parcel which weighs 10kg is added to the box, the average mass becomes 18kg. How many parcels are in the box now ?

Refer to http://www.onsponge.com/index.php?option=com_kunena&Itemid=282&func=view&id=11322&catid=35#11322 and you should be able to work out the answer as 5 parcels are in the box now.

kavisuresh:

3. At an enrichment camp, the number of boys was 45% of the number of girls. When 20% of the boys left the camp, there were 192 more girls than boys. How many children were at the camp at first ?

Before
B : G
45 : 100
9 : 20

After
7.2 : 20

20u-7.2u=12.8u = 192
u = 15

At first, number of children at the camp = 9u+20u = 29u = 29x15 = 435.

[raghupavithra]

John had a sum of money. On Monday, he spent 25% of his money. On Tuesday, he spent 1/3​ of his money. On Wednesday, he spent 25% of what he spent on Monday and Tuesday. If he had $39 left, how much did he have at first?



how to do this.pls help me?

[Vanilla Cake]

raghupavithra:

John had a sum of money. On Monday, he spent 25% of his money. On Tuesday, he spent 1/3​ of his money. On Wednesday, he spent 25% of what he spent on Monday and Tuesday. If he had $39 left, how much did he have at first?

Refer to Uncle tianzhu's solution.

[tianzhu]

raghupavithra:

John had a sum of money. On Monday, he spent 25% of his money. On Tuesday, he spent 1/3​ of his money. On Wednesday, he spent 25% of what he spent on Monday and Tuesday. If he had $39 left, how much did he have at first?



how to do this.pls help me?

Hi

You may use UM or MD.

Draw a bar of 48 units.

Mon ----- 12 units (25% 0f 48))

Tues ----- 16 units (1/3 of 48)

Wed -----7 (25% of 28)

Left ------ 48 -35 ------13 units

13 units ------39

1 unit ------3

48 units ------144

Best wishes

[tianzhu]

Hi VC


Please refer to your PM.

Best wishes

[tianzhu]

raghupavithra:

how solve this Express $1 as a percentage of 25-cents.


400%
25%
20%
4%

Hi

$1 is 4 times of 25 cents.

Percentage ------4/1*100 -------400%

or 100/25*100 -------400%

Best wishes

[Vanilla Cake]

P5G:

My answer for question 10 is 49.16 kg (correct to 2 decimal places).I minus 3 x 15 from the total weight since the bathroom scale shows 5 kg, which I interprete it to mean each reading will be 5 kg more.

The question does not state to round off the answer, so I correct it to 2 decimal places

http://i53.tinypic.com/29dtmki.png\">
72.6x3-15=202.8

B : A
2 : 3

C : B
4 : 5

B : A : C
10 : 15 : 8

202.8/33x8 = 49.163.... kg = 49.16 kg (2 decimal places)
Yes, this should be the correct answer.

[raghupavithra]

how to get 48

[raghupavithra]

how solve this Express $1 as a percentage of 25-cents.


400%
25%
20%
4%

Hi

$1 is 4 times of 25 cents.

Percentage ------4/1100 -------400%

or 100/25100 -------400%

Best wishes


no they put answer is 20 how i get this answer