Question

за контрольную работу 1/6 часть класса получила пятерки, 8/15 -четверки,троек было на 10 меньше,чем четверок,а двоек-3. какой процент учеников класса написал на «4» и «5»? сколько было четверок,а сколько - пятерок?помогите срочно! Пожалуйста

Answer 1

Пусть х - это кол-во учеников в классе,тогда
1/6*х - пятерки
8/15*х - четверки
8/15*х - 10 - троек
3 - двойки
1/6х + 8/15х +8/15х - 10 + 3 = х
5/30*х + 16/30*х + 16/30*х - 30/30*х = 10-3
7/30*х = 7
х=30
в классе 30 учеников
1/6 - пятерки это 5 учеников
8/15 - четверки это 16 учеников
вместе это 21 ученик
21 ученик т.е  от 30 это 70%
Ответ: 70 процентов учеников класса написали контрольную на 4 и 5

Answer 2

Problem Analysis

To solve this problem, we need to determine the percentage of students in the class who received a grade of "4" or "5" and find the number of students who received a grade of "4" and "5". We are given the following information: - 1/6 of the class received a grade of "5". - 8/15 of the class received a grade of "4". - The number of students who received a grade of "3" was 10 less than the number of students who received a grade of "4". - There were 3 students who received a grade of "2".

Let's solve this step by step.

Solution

Step 1: Calculate the total number of students in the class. To find the total number of students in the class, we need to find the least common multiple (LCM) of 6 and 15, as these are the denominators of the fractions given. The LCM of 6 and 15 is 30.

Step 2: Calculate the number of students who received a grade of "5". Since 1/6 of the class received a grade of "5", we can calculate the number of students using the following formula: Number of students who received a grade of "5" = (1/6) * Total number of students

Step 3: Calculate the number of students who received a grade of "4". Since 8/15 of the class received a grade of "4", we can calculate the number of students using the following formula: Number of students who received a grade of "4" = (8/15) * Total number of students

Step 4: Calculate the number of students who received a grade of "3". The number of students who received a grade of "3" is 10 less than the number of students who received a grade of "4". We can calculate the number of students using the following formula: Number of students who received a grade of "3" = Number of students who received a grade of "4" - 10

Step 5: Calculate the number of students who received a grade of "2". We are given that there were 3 students who received a grade of "2".

Step 6: Calculate the percentage of students who received a grade of "4" or "5". To calculate the percentage, we need to divide the sum of the number of students who received a grade of "4" and "5" by the total number of students and multiply by 100.

Let's calculate the values step by step.

Step 1: Calculate the total number of students in the class. The LCM of 6 and 15 is 30, so the total number of students in the class is 30.

Step 2: Calculate the number of students who received a grade of "5". Number of students who received a grade of "5" = (1/6) * 30 = 5

Step 3: Calculate the number of students who received a grade of "4". Number of students who received a grade of "4" = (8/15) * 30 = 16

Step 4: Calculate the number of students who received a grade of "3". Number of students who received a grade of "3" = 16 - 10 = 6

Step 5: Calculate the number of students who received a grade of "2". Number of students who received a grade of "2" = 3

Step 6: Calculate the percentage of students who received a grade of "4" or "5". Percentage = ((Number of students who received a grade of "4") + (Number of students who received a grade of "5")) / Total number of students * 100 Percentage = (16 + 5) / 30 * 100 = 21/30 * 100 = 70%

Answer

Based on the given information, 70% of the students in the class received a grade of "4" or "5". There were 16 students who received a grade of "4" and 5 students who received a grade of "5".