Вопрос школьника по предмету Математика
сколько существует пятизначных чисел, произведение двух последних цифр которых равно 21?
Ответ учителя по предмету Математика
Пятизначных чисел всего 90000, произведение последних двух цифр это 3*7=7*3=21, то есть в каждой сотне есть всего два таких числа.
В пятизначных числах 90000/100=900 сотен.
900*2=1800 таких чисел.
Похожие вопросы от пользователей
1) хлорид натрия
2) хлороводород
3) фтор
4) оксид хлора (1)
Иероглифы,брахманы,клинопись,полис,потриции,конфуцианство.
1) My friend (to come) back from business trip yesterday. Our teacher (to ask) me twice today.
2) The plane just (to land). He (to give) me his notes last week.
3) She (to send) three letters to this firm already. They (to do) the exercises quickly yesterday.
4) The workers (to go) to the meeting already. He (to ask) many questions last lesson.
5) I (to speak) with my boss already. They (to go) to the seaside by train last summer.
6) She (to leave) the keys at home today. They (to buy) new equipment last month.
7) They (to pass) all the exams already. He (to open) the window 20 minutes ago.
8) I (to study) at school five years ago. My friends just (to see) a very interesting film.
9) Her sister (to clean) the window last week. My father (to buy) a new car this month.
10) The birds (to fly) to the south already. We (to close) the door five minutes ago.