Disclaimer: This article is open for discussion. I have bought this reference book for Secondary 1 Express Mathematics, fourth reprint 2012, 2nd Edition, and found some questionable examples.
In the above extract from Page 12, it is a question for the readers to solve. Let’s do it together:
(a) The difference in the sea level between high tide and low tide = 2 + 4 = 6 m
(b) When the sea level is exactly halfway between high tide and low tide, it is 3 m from either tide.
The sea level is (4 – 3) m = 1 m below the clam at this time.
Below is the extract from Page 123, the answer in the book for question 20.
Answer (b) is different from what I have done. From the calculation of the sea level, it is 3 m, which is the same as my answer. Thus, from the picture above, even without calculation, we can deduce that the sea level is 1 m below the clam when the sea level is exactly halfway between high tide and low tide.
With this example and another example on factors and multiples, I hope parents and students will be careful when referring to any reference books available in the market. If you have any doubt, always find a third opinion. Most importantly, have confidence in yourself, do not feel discouraged if your answers are different. Knowledge is gained through questioning.
I am not sure if they have rectified the error, just want to alert parents and students if you have bought the same book with the same version as mine. I welcome comments and feedback. Thank you.