## Wednesday, April 25, 2012

### P6 Circles (fr Sean)

[Question taken from: Raffles girls SA1 2010]

## Saturday, April 21, 2012

### P6 Ratio [Heuristics: Guess-and-check, Algebra, Sakamoto ]

A coin box contained only twenty-cent and fifty-cent coins in the ratio of 4:5. When 16 fifty-cent coins were taken out and replaced by some twent-cent coins, the number of fifty-cent coins left in the box was 7/8 of the twenty-cent coins. The total value of all the coins remained the same. Find the sum of money in the coin box.
[Ai Tong Pr School of 2011]

My solution:

From Jayden

From Jayden

From Jayden

## Saturday, April 14, 2012

### P6 Ratio "External transfer" (heuristics: algebra, sakamoto)

Alina and Adeline had some stickers in the ratio 3:5.When Alina bought 42 more stickers and Adeline bought 7 more stickers,the ratio became 6:7.Find the number of stickers Alina had at first.

## Friday, April 13, 2012

### Whole numbers (heuristics: model)

The mass of a book and a bag is 7kg altogether.The mass of the same book and a box is 11kg.The mass of the bag and the box is 14kg.Find the mass of the box.

### P6 Speed.

Simon intends to drive to attend an appointment at 8pm.
If he drives at 75 km/h, he will be 13 minutes late.
If he drives at 115 km/h, he will be 11 minutes early.
If he wants to be exactly on time for his appointment,
(a) at what speed should he drive? (Give your answer correct to 2 decimal places)
(b) at what time must he start driving at the speed in (a)?

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## Thursday, April 12, 2012

### Whole numbers, Fractions (Heuristics: Model, algebra, sakamoto method)

Max had \$9 and Alan had \$6.  Max spent twice as much as Alan and was left with half as much as Alan.  How much did Alan spend?

### Perimeter

 Nanyang SA1 (2011)