Cho tam giác ABC, điểm M thuộc cạnh BC sao cho M B M C = 1 2 . Đường thẳng đi qua M và song song với AC cắt AB ở D. Đường thẳng đi qua M và song song với AB cắt AC ở E. Biết chu vi tam giác ABC bằng 30cm. Chu vi của các tam giác DBM và EMC lần lượt là

A. 10cm; 15cm

B. 12cm; 16cm

C. 20cm; 10cm

D. 10cm; 20cm

Read and answer the questions.

Hello! I am Jerry. I am 13 years old. I live a country house. There are 4 people in my family: my father, my mother, my elder sister and I. My father is 42 years old and he is an engineer. My mother is 40 years old. She is a farmer. My sister is seventeen. She is a student. And I am a student in grade 6 in Newton secondary school. My school is small but it is very nice. There are 23 students in my classroom: 15 boys and 8 girls. Every day I get up at six o’clock. Then I go to school at seven o’clock.

How many students are there in his classroom?