Age is a common type of question in our line test exam, which mainly examines the students' grasp and analysis of the quantitative relationship in the process of age change, and is also a special need for students to pay attention to in solving the problem。
It is known that the sum of the ages of Xiao Ming's parents this year is 76 years old, and the sum of the ages of Xiao Ming and his younger brother is 18 years old. Three years later, his mother was three times the age of Xiao Ming, and his father was four times the age of Xiao Ming's younger brother. How old is Xiao Ming this year?（
a．11 b．12 c．13 d．14
This question gives the following quantitative relationships: the sum of the ages of the parents this year, the sum of the ages of Xiao Ming and his younger brother this year, and the multiple relationship between the age of the mother and Xiao Ming after 3 years, and the multiple relationship between the age of the father and the younger brother.
Method 1: Find out who sets the law.
Advantages: What the question asks and what is set, and finding it is the answer directly.
Disadvantages: The calculation process is complex.
According to the title, if Xiao Ming is x years old this year, then his younger brother is 18-x this yearAfter 3 years, Xiao Ming x+3, younger brother 21-x, mother 3 (x+3), father 4 (21-x), since the sum of the parents' ages this year is 76, so the sum of the parents' ages after 3 years is 76+6=82, so the equation is listed 3 (x+3) + 4 (21-x) = 82, and the solution is x=11
Method 2: Set the number of copies.
Advantages: The use of multiples off series is fast, and the calculation is simple.
Disadvantages: The answer is not directly needed by the question, you need to add or subtract again, and it is easy to fall into your own trap.
According to the mother's age is 3 times that of Xiao Ming after 3 years, and the father's age is 4 times that of the younger brother, if Xiao Ming's age is x after 3 years, and the younger brother's age is y after 3 years, then the mother's age after 3 years is 3x, and the father's age is 4y;According to the sum of the ages of Xiao Ming and his younger brother this year is 18, and the sum of the ages of his parents is 76, the sum of the ages of Xiao Ming and his younger brother after 3 years is 18 + 6 = 24, and the sum of the ages of the parents is 76 + 6 = 82, so the column formula x + y = 24, 3x + 4y = 82, and the solution is x = 14, but it should be noted that x here is Xiao Ming's age after 3 years, so Xiao Ming is 14-3 = 11 this year
Through the above examples, we have a further understanding of the skills of setting elements in age problems, so after mastering a lot of problem solving methods, students should choose the method that suits them according to the situation, so as to be fast and accurate in the examination room, and succeed immediately!