This blog is managed by Song Hock Chye, author of Improve Your Thinking Skills in Maths (P1-P3 series), which is published and distributed by EPH.

Friday, January 30, 2009

Tao Nan School P5 SA2 2007 Math Q45

Kate has some stickers. If she gives her friends 7 stickers each, she will have 3 stickers left. If she gives them 8 stickers each, she will be short of 6 stickers.

a) How many friends does she have?
b) How many stickers does she have?

Solution




The difference in number of stickers is 9. This 9-sticker difference is due to each of her friend receiving 1 more sticker. Hence, she has 9 friends, receiving 1 more sticker each.

Answer: She has 9 friends.


(b)
7 stickers to 9 friends ----- 9 x 7 = 63
Add 3 extra stickers ----- 63 + 3 = 66

Answer: She has 66 stickers.

Wednesday, January 28, 2009

Appeal for Aid on behalf of war victims

http://www.dec.org.uk/item/200

The situation

After an 18 month blockade of Gaza and three weeks of heavy shelling the humanitarian crisis in Gaza is now completely overwhelming.

- Thousands of people are struggling to survive with many having lost their homes and most down to their last supplies of food and only limited amounts of fresh drinking water.

- Just £25 can buy warm blankets for 8 children

- Just £50 can provide a Food parcel for a family for one month

Electricity - supplies to Gaza are erratic at best with 75% of the area cut off completely. There is a significant public health risk arising out of the almost collapse of Gaza’s water and sewage system, the running of which is dependent on electricity.

Water - Around 500,000 people are without running water with 37% of Gaza’s water wells not working effectively and fuel reserves depleted due to restrictions on access and damage to pipes.

- At least 412 Children have been killed and 1,855 injured

- 60% of the population is living in poverty

- 1.1 million people are dependent upon aid to survive.

Health - The capacity of the health system has been significantly reduced due to the damage of at least 21 clinics. Ten primary health care clinics are functioning as emergency clinics and hospitals and intensive care units continue to treat the mass casualties.

http://www.dec.org.uk/donate_now/

http://www.dec.org.uk/faq/

Tao Nan School P5 SA2 2007 Math Q44

ACEG is a square, not drawn to scale. Lines DF, CG and BH are parallel lines. Angle EFD is 45 degrees. Calculate
a) Angle CDF

b) Angle AHB



Solution

a)
Angle EDF = (90 – 45) degrees
= 45 degrees

Angle CDF = (180 – 45) degrees
= 135 degrees (Answer)


b)
Angle EFD = Angle AHB = 45 degrees (Answer)

Wednesday, January 21, 2009

Tao Nan School P5 SA2 2007 Math Q43

The ratio of Liling’s money and Yingqi’s money was 7:4. When Liling gave $100 to Yingqi, the ratio became 5:6. How much money did Liling have at first?

Solution

Liling : Yingqi
7 : 4 (before ----- 11 units)
5: 6 (after ----- 11 units)

As can be seen from above, 2 units were given.

2 units ----- $100
1 unit ----- $100 divided by 2 = $50

(Liling at first) 7 units ----- 7 x $50 = $350

Answer: Liling had $350 at first.

Tuesday, January 20, 2009

Vocabulary – Satire

Satire: the use of irony, sarcasm, ridicule, or the like, in exposing, denouncing, or deriding vice, folly, etc.

A picture is worth a thousand words. A video clip is worth a million.

Below is an example of satire. Today is US President GW Bush’s last day at the White House. Observe the sarcasm and ridicule played out.

Monday, January 19, 2009

Tao Nan School P5 SA2 2007 Math Q42

A rectangular fish tank 80 cm long and 60 cm wide is filled with water from a tap which flows at a rate of 3 litres per minute. If the tap is turned off after 40 minutes, what is the height of the water level in the container?

Solution


1 minute ----- 3 litres or 3000 ml
40 minutes ----- 40 x 3000 ml
= 120 000 ml or 120 000 cubic cm

Height of water level -----

Volume = length x base x height
120 000 cubic cm = 80 cm x 60 cm x height
120 000 cubic cm = 4800 square cm x height
Height = 120 000 cubic cm divided by 4800 square cm
Height = 25 cm (Answer)

Friday, January 16, 2009

Tao Nan School P5 SA2 2007 Math Q41

Lily and Kumar had an equal number of marbles. After a game, Lily lost 20 of her marbles. Lily then had 1/3 as many marbles as Kumar. How many marbles did each of them had at first?

Solution



2 units ----- 20
1 unit ----- 20 divided by 2 = 10
3 units ----- 3 x 10 = 30

Answer: They had 30 marbles each at first.

Wednesday, January 14, 2009

Tao Nan School P5 SA2 2007 Math Q40

WXYZ is a rectangle. Find the area of the shaded part.



Solution

Area of rectangle ---- 12 cm x 6 cm = 72 square cm

Area of unshaded triangle ----
½ x base x height
= ½ x 7 cm x 6 cm = 21 square cm

Area of shaded part -----
(72 – 21) square cm= 51 square cm (Answer)

Tuesday, January 13, 2009

Common Errors and confusion – Cell Division

Cell division is the process where the cell splits into two new cells. What is the purpose of cell division? That depends on:

If the organism is a multi-cellular organism, (for example a cat, a mango tree, a mushroom) the purpose is for growth and replacement of old cells. A kitten needs to grow into a cat. A seedling needs to grow into an adult plant. Hence, cells need to go through the process of cell division so that the organism can grow. Cell division also helps replace older cells that die.

If the organism is a single-cellular organism, (for example paramecium, bacterium) the purpose is for reproduction. All living things reproduce more of their own kind for the continuity of their specie.

The most common confusion among students is that they erroneously think that the purpose of cell division is for growth, replacement of old cells and reproduction for all organisms. This concept is WRONG.

Below, is a table that summarises the right and wrong concepts of the function of cell division.

Tao Nan School P5 SA2 2007 Math Q39

There are some pigs, cows and goats in a farm. The ratio of the number of pigs to the number of cows is 3 : 4. The ratio of the number of cows to the number of goats is 2 : 3. What is the ratio of the number of pigs to the total number of animals in the farm?

Solution



Pigs ----- 3 units
Total ----- 13 units

Pigs : Total
3 : 13

Answer: The ratio of number of pigs to the total number of animals is 3:13

Sunday, January 04, 2009

Tao Nan School P5 SA2 2007 Math Q38

If Premila withdraws $150 from her savings account, she will have $450 left. What fraction of her savings should she withdraw so that she will have $75 left? Express your answer in the simplest form.

Solution



Fraction that is needed to be withdrawn -----
$525 divided by $600 = 7/8

Answer: The fraction of her savings that she should withdraw is 7/8.

Thursday, January 01, 2009

Free Nan Hua P6 CA1 2007 Math Worked Solutions

HAPPY NEW YEAR 2009 TO ALL

A new set of free Maths worked solutions (Section C only) is now ready.

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