Question

1.Найдите разность 7/20 и 11/15 2.Вычеслить: 3-2(целых)3/4; 14(целых)4/5:7(целых)3/4 3.В классе 30 ученкинов, 25% изучают астрономию. Сколько человек не изучают астрономию? 4.Упростить: 2*(7х-1)-3*(5*2х) 5.Найдите неизвестный член пропорции: 3,6:х=6:1,2 20 БАЛОВ!!!11!!1

Answer 1

1. =21/60-44/60=-23/60
2. 1/4; = 74/5:31/4=296/155
3. 75%=30*3/4= 22,5 (Но такого не может быть)
4. 14x-2-30x=-16x-2
5. x=3,6*1,2/6= 0,72

Answer 2

1. Найдите разность 7/20 и 11/15: To find the difference between two fractions, we need to have a common denominator. In this case, the least common multiple of 20 and 15 is 60. Let's convert the fractions to have a denominator of 60: 7/20 = (7/20) * (3/3) = 21/60 11/15 = (11/15) * (4/4) = 44/60

Now that we have both fractions with a common denominator, we can subtract them: 21/60 - 44/60 = (21 - 44)/60 = -23/60

So, the difference between 7/20 and 11/15 is -23/60.

2. Вычислить: 3 - 2(целых)3/4; 14(целых)4/5 : 7(целых)3/4: To simplify the expressions, let's break it down step by step:

3 - 2(целых)3/4: First, we multiply 2 by 3/4: 2 * 3/4 = 6/4 = 3/2

Now, we subtract 3/2 from 3: 3 - 3/2 = (6/2) - (3/2) = 3/2

So, the result is 3/2.

14(целых)4/5 : 7(целых)3/4: First, let's convert the mixed numbers to improper fractions: 14(целых)4/5 = (14 * 5 + 4)/5 = 74/5 7(целых)3/4 = (7 * 4 + 3)/4 = 31/4

Now, we divide 74/5 by 31/4: (74/5) / (31/4) = (74/5) * (4/31) = (74 * 4) / (5 * 31) = 296/155

So, the result is 296/155.

3. В классе 30 учеников, 25% изучают астрономию. Сколько человек не изучают астрономию? To find the number of students who do not study astronomy, we need to calculate 75% of the total number of students:

75% of 30 = (75/100) * 30 = (3/4) * 30 = 22.5

Since we can't have a fraction of a student, we round the result to the nearest whole number:

The number of students who do not study astronomy is approximately 23.

4. Упростить: 2*(7х-1)-3*(5*2х) To simplify the expression, let's perform the operations step by step:

2*(7х-1) - 3*(5*2х): First, let's simplify the expression inside the parentheses: 7х - 1

Now, let's simplify the expression inside the second set of parentheses: 5 * 2х = 10х

Now, let's substitute these simplified expressions back into the original expression: 2*(7х - 1) - 3*(10х)

Next, let's distribute the coefficients to each term inside the parentheses: 2*7х - 2*1 - 3*10х

Simplifying further: 14х - 2 - 30х

Now, let's combine like terms: 14х - 30х - 2

Finally, let's simplify the expression: -16х - 2

So, the simplified expression is -16х - 2.

5. Найдите неизвестный член пропорции: 3,6:х = 6:1,2 To find the unknown term in the proportion, we can cross-multiply:

(3,6 * 1,2) = (6 * х) 4,32 = 6х

Now, let's solve for х by dividing both sides of the equation by 6: 4,32 / 6 = х

Simplifying the division: 0,72 = х

So, the unknown term in the proportion is х = 0,72.

Please note that in mathematical expressions, the decimal separator is a dot (.), not a comma (,). In the calculations above, I used a comma as a decimal separator to match the format of your question, but in formal mathematics, a dot should be used.