Q&A - PSLE Math

[MathIzzzFun]

SAHM88:

Please help!

1. There were 1000 students at the parade ground and indoor sports hall. 40% of the 600 students at the parade ground were girls. 60% of the students at the indoor sport hall were girls. After some students in both venues moved from one venue to the other, 30% of the students in the parade ground and 70% of the students at the indoor sports hall were girls. How many students were there in the indoor sports hall after the movement had taken place?

2. A large warehouse had a total of 2180 black, red and white T-shirts for sales. The ratio of the number of black T-shirts to the number of red T-shirts was 3:1. After 2/5 of the black T-shirts, 1/3 of the white T-shirts and none of the red T-shirts were sold on the first day, there were 1504 T-shirts left. How many red T-shirts did the warehouse have at first?

Thanks

Q1.
this was discussed before - http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&p=777637&hilit=1000+students#p777637

it is similar to the Apples and oranges question, one post before this.



Q2.
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&p=781608&hilit=2180+black#p781608


cheers.

[mlim321]

Thanks tianzhu for the clarification!

[Easy-going]

Beaker A and Beaker B contain some water. If 46.5ml of water is drained from Beaker A, the volume of the water in beaker A will be 60% that of the water in Beaker B.

If 35.2 ml of water is drained out from Beaker B, the volume of the water in Beaker B will be 85% that of the water in Beaker A.
What is the tota volume of water in Beaker and Beaker B?

[its888me]

The figure below shows 3 different rectangles, X, Y and Z. 3/10 of X and 40% of Z is shaded. The shaded area of X is the same as the shaded area of Z. What fraction of the figure is unshaded if 60% of Y is shaded?


My child got the answer 4/7, but the answer is 31/43. What is wrong? Can someone help? Thanks! http://i49.tinypic.com/15dlah.jpg\">

[MathIzzzFun]

its888me:

The figure below shows 3 different rectangles, X, Y and Z. 3/10 of X and 40% of Z is shaded. The shaded area of X is the same as the shaded area of Z. What fraction of the figure is unshaded if 60% of Y is shaded?


My child got the answer 4/7, but the answer is 31/43. What is wrong? Can someone help? Thanks! http://i49.tinypic.com/15dlah.jpg\">

Hi

X, shaded:unshaded = 3 : 7 --> 6 units: 14 units
Z, shaded:unshaded = 2 : 3 --> 6 units: 9 units
Y, shaded:unshaded = 3 : 2 --> 12 units : 8 units --- Y, total --> 20 units
total unshaded --> (14 + 9 + units = 31 units
total area --> 14 units (X, unshaded) + 9 units (Z, unshaded) + 20 units (Y) = 43 units
fraction of figure that is unshaded = 31/43

cheers.

[tanpk]

Hi


Need a help on the question below. Wondering if any one can help? Its a foundational math qn, it seem hard. Thanks!

Question
A restaurant had the same number of apples, oranges and pears at first. After 38 pears, some apples and oranges were used, there were 90 fruits left. There are twice as many apples as oranges left.
The number of pears left were 15 fewer than the number of apples left.

(a) How many pears were left?
(b) How many apples, oranges and pears were there altogether at first?

[lizawa]

[quote]Hi


Need a help on the question below. Wondering if any one can help? Its a foundational math qn, it seem hard. Thanks!

Question
A restaurant had the same number of apples, oranges and pears at first. After 38 pears, some apples and oranges were used, there were 90 fruits left. There are twice as many apples as oranges left.
The number of pears left were 15 fewer than the number of apples left.

(a) How many pears were left?
(b) How many apples, oranges and pears were there altogether at first?[/quote]At first
A : O : P
1 : 1 : 1

After
2p : 1p : 1u -38

90 fruits left, so
3p + 1u -38 = 90
3p + 1u = 128
1u = 128 - 3p


Pears were 15 fewer than apples

2p - 15 = 1u - 38
1u = 2p + 23

Solve the 2 equations
1p = 21
1u = 65

a) pears left -> 65 - 38 = 27
b) at first -> 3u = 195

[jarenchuatw]

Help needed for these 2 questions - many thanks in advance!


1. Mr Rani and Mr Chau drove along the same route from City X to City Y. Ms Rani took 12 hours while Mr Chua took 9 hours to complete the whole journey. Their difference in their average sped was 15 km/hr.
a) What was the distance between the 2 towns?
b) What was the average speed of Mr Chua?

2. A block of wood 40cm by 14cm by 8 cm was cut into smaller pieces which were 7cm by 6cm by 2cm each. What was the maximum number of pieces that it could be cut into?

[lizawa]

[quote]Help needed for these 2 questions - many thanks in advance!


1. Mr Rani and Mr Chau drove along the same route from City X to City Y. Ms Rani took 12 hours while Mr Chua took 9 hours to complete the whole journey. Their difference in their average sped was 15 km/hr.
a) What was the distance between the 2 towns?
b) What was the average speed of Mr Chua?[/quote]Common distance question. Use ratio of speed and time to solve
TR : TC
12 : 9
SR : SC
9 : 12

3u -> 15
1u -> 5
speed of Rani -> 5 * 9 = 45 km/h
Distance = 45 * 12 = 540 km

Speed of chua -> 12 * 5 = 60km/h

[lizawa]

[quote]Help needed for these 2 questions - many thanks in advance!

2. A block of wood 40cm by 14cm by 8 cm was cut into smaller pieces which were 7cm by 6cm by 2cm each. What was the maximum number of pieces that it could be cut into?[/quote]Need to maximize each side of the wood.

Place 7cm on the 14cm side. 2cm on the 8cm side. 6cm on the 40 cm side.

You get 2 *4 * 6 = 48