Wednesday, April 25, 2012

P6 Circles (fr Sean)

[Question taken from: Raffles girls SA1 2010]

Click here for my solution

Sunday, April 22, 2012

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:

P6 Ratio (fr jayden)

From Jayden

P6 Ratio (fr jayden)

From Jayden

P6 Circle (fr jayden)

From Jayden

P6 Ratio (heuristic: algebra

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)?

Click here for my solution

P6 fraction (heuristics: algebra)

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?


Nanyang SA1 (2011)