On June 6 and 7, nearly 96,000 candidates took the Literature, Foreign Language, and Math exams to compete for a place in grade 10 public schools in Ho Chi Minh City. Teachers commented that the Math exam had the same structure and difficulty as last year. The exam had 5 practical problems, from question 3 to question 7.

After the exam ended, Mr. Mai Van Tuc, a Physics teacher at the High School for the Gifted in Natural Sciences, Hanoi National University, said that question 5 in the 10th grade Math exam of Ho Chi Minh City presented a rule that does not exist in reality and is fundamentally wrong.

Specifically, the process of energy conversion when boiling water is calculated from the moment the switch is turned on (at t = 0); electrical energy is converted into heat energy, making the heating wire hot (if the kettle uses a heating wire). The heating wire has a higher temperature than the water in the kettle and transfers heat to the water, the water transfers heat to the kettle and it takes a period of time for the heat to be lost to the environment. The heat loss capacity to the environment depends mainly on the contact area of ​​the kettle with the environment and the temperature difference between the temperature of the kettle and the environment (the loss capacity also depends on the level of air circulation or wind in the place of heating). When the heat loss capacity to the environment of the kettle is equal to the power received by the heating wire, the temperature of the water will no longer increase.

Teacher Tuc gave an example of a heating wire with a capacity of 1,000 W. If water is boiled in a 2-liter kettle, the water can boil, but if this heating wire provides heat for a large fish tank, the water can only heat from 10 degrees Celsius to 30 degrees Celsius, then the temperature will not increase anymore. At that time, the power loss remains constant and is equal to the power consumption of the heating wire of the kettle. So question 5 gives the power loss according to the rule P = at + b, that is, t = 0, the power loss is equal to 85 W and the power loss increases steadily, which is wrong. The teacher also thinks that the question is wrong when asking "If water is boiled with a power loss of 105 W, how long will it take to boil?". If we assume that there is an illogical rule as the author gives, we need to ask: Calculate the boiling time until the power loss is 105 W.

With these arguments, Mr. Tuc proposed that the HCM City Department of Education and Training adjust the answer to question 5 to ensure fairness for candidates. This teacher believes that students who are good at Physics may not be able to do question 5 when the data in the question is too strange.

Meanwhile, Mr. Lam Vu Cong Chinh, a Math teacher at Nguyen Du High School, Ho Chi Minh City, said that if we consider Physics knowledge and reality, the data in question 5 is not reasonable and logical. However, if the question is just a survey, synthesis and giving a prediction formula, not an exact Physics formula, it is still acceptable.

Mr. Chinh gave an example of estimating population growth. According to him, this is a problem for which there is no absolutely accurate formula, however, experts still apply a formula according to certain rules and facts to predict and estimate future population.

"If students apply mathematical knowledge, they can still solve the problem normally. This error does not affect the test results of the candidates," said Mr. Chinh.

Ms. Nguyen Tien Thuy, a math teacher at Ha Huy Tap Secondary School, Ho Chi Minh City, commented that question 5 is in the form of a first-degree function. The question gives the formula for the first-degree function with clear formulas for each quantity and unit, along with graphical illustrations, so students can solve it normally.

On June 9, the Ho Chi Minh City Department of Education and Training said that question 5 of the 10th grade math exam included content related to the real phenomenon of the process of boiling water in an electric kettle. This survey process is only a short stage of the water boiling process and the time when the survey started (t = 0) is not the time when the water boiling process started.

With the data surveyed in this process, mathematically it can be described as a drawing and by a function that students have learned in the program. Therefore, with mathematical knowledge and ability (first-degree function, graph of first-degree function, points on graph, system of first-degree equations with two unknowns, calculation) students can solve the requirements set by the problem.

"In cases where students have solutions that are different from the grading instructions but reasonable, they will be considered and evaluated," the Department of Information said.

Last year, about 45% of candidates taking the 10th grade entrance exam in Ho Chi Minh City scored below average in Math.

This year, Ho Chi Minh City has about 96,000 students taking the 10th grade entrance exam at public schools. The total enrollment target for the city’s 108 public high schools is 77,300, with an admission rate of about 80%. The Department of Education and Training said the exam scores will be announced on June 20.

Le Nguyen