Ho Chi Minh City Department of Education and Training responds

On the afternoon of June 9, information from the Department of Education and Training of Ho Chi Minh City, based on public opinion about the "errors" in the 10th grade entrance math exam question 5, the Department has reviewed and responded.

Specifically, the problem presents content related to the real phenomenon of the process of boiling water in an electric kettle. This investigation process is only a short stage of the water boiling process; the time at which the investigation begins (t = 0) is not the time when the water boiling process begins.

Lesson 5 Math exam for grade 10 public schools in Ho Chi Minh City, school year 2023-2024.

With the data surveyed in this process, mathematically it can be described as a drawing and represented by the 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 question.

"According to the regulations and instructions for grading, cases where students have solutions that are different from the instructions but reasonable will be considered and evaluated," the Department of Education and Training of Ho Chi Minh City emphasized.

Previously, after the 10th grade entrance exam for the 2023 - 2024 school year ended, some comments said that question 5 of this exam had errors in Physics knowledge such as: The question gives the power P with the accompanying unit W, then the coefficients a, b in the formula P = at + b must have corresponding units W/s and W. If the student's answer or solution only gives the number, but lacks the unit, it is incorrect.

If we understand it as finding the time t from t = 0 so that P (t) = 105W, then the data "boiling water" is misleading and irrelevant to the problem. If we still understand it as finding the time to boil water with a power of 105W, many problems arise. Suppose we boil m (kg) of water from T1 (degrees C) to T2 (degrees C), the specific heat capacity C (J/kgC), then the heat required is Q = mc (T2-T1).

To write boiling water with fixed power is misleading, because of the lack of data on starting temperature, water mass, specific heat capacity of water. Moreover, solving in this direction has nothing to do with the given function P(t), but only applies to calculating work W = Pt = 105.t and solving the equation Q = W and finding the unknown t.

Because the power P(t) changes with time t, the formula to be followed is W = integral [ P(t') dt'] from t' = 0 to t' = t (the time to be found) and solving for Q = W is implicit in t. Understood this way, the integral knowledge is outside the program and the 105 W data becomes ambiguous.

In addition, with the data provided in the exam, if applying the formula it can be solved, but if analyzing more deeply from a Physics perspective it can make students confused.

Lam Ngoc

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Source: https://vtc.vn/de-thi-toan-lop-10-co-san-so-gd-dt-tp-hcm-phan-hoi-ar798578.html