Question

1.а)3/10 - 2/15 б)3,25*50,6 2.шесть рабочих могут выполнить работу за 15 дней.За сколько дней выполняют эту работу 10 рабочих,если будут работать с такой же производительностью?3.Вычислите: 3/8 : 7/12 + 3 1/7 * 3/11 4.Найдите значение выражения 0,3а-7 при а= -5 5.В магазин привезли печенье.В первый день продали 52 кг печенья,а во второй день-в 1,3 раза меньше,чем в первый.Сколько килограммов печенья привезли в магазин,если за два дня продали 1/3 привезенного печенья

Answer 1

1.а)3/10-2/15=9/30-4/30=5/30=1/6
б)3,25*50,6 =164,45
3.3/8:7/12+4/7*311=9/14+12/77=(99+24)/154=123/154
4.0,3*-5-7=-8,5

Answer 2

1.а) To add fractions with different denominators, we need to find a common denominator. The common denominator for 10 and 15 is 30.

3/10 + 2/15 = (3/10) * (3/3) + (2/15) * (2/2) = 9/30 + 4/30 = (9 + 4)/30 = 13/30

So, the sum of 3/10 and 2/15 is 13/30.

б) To multiply decimal numbers, we can simply multiply the numbers as if they were whole numbers and then adjust the decimal point.

3.25 * 50.6 = 164.35

So, the product of 3.25 and 50.6 is 164.35.

2. If six workers can complete a job in 15 days, we can use the concept of "worker-days" to solve this problem. The total number of worker-days required to complete the job is constant.

Let's assume the total number of worker-days required to complete the job is X.

6 workers * 15 days = 10 workers * X days

To find X, we can set up a proportion:

6 * 15 = 10 * X

90 = 10X

X = 9

So, 10 workers can complete the job in 9 days if they work at the same productivity rate.

3. To simplify the given expression:

3/8 : 7/12 + 3 1/7 * 3/11

To divide fractions, we multiply the first fraction by the reciprocal of the second fraction.

3/8 : 7/12 is the same as 3/8 * 12/7 = 36/56 = 9/14

Next, we convert the mixed number 3 1/7 to an improper fraction:

3 1/7 = (3 * 7 + 1) / 7 = 22/7

Now, we can evaluate the expression:

9/14 + 22/7 * 3/11

To multiply fractions, we multiply the numerators together and the denominators together:

= 9/14 + (22 * 3) / (7 * 11) = 9/14 + 66/77

To add fractions with different denominators, we need to find a common denominator. The common denominator for 14 and 77 is 154.

= (9 * 11) / (14 * 11) + (66 * 2) / (77 * 2) = 99/154 + 132/154 = (99 + 132) / 154 = 231/154

So, the value of the expression 3/8 : 7/12 + 3 1/7 * 3/11 is 231/154.

4. To find the value of the expression 0.3a - 7 when a = -5:

0.3a - 7 = 0.3(-5) - 7 = -1.5 - 7 = -8.5

So, the value of the expression 0.3a - 7 when a = -5 is -8.5.

5. Let's denote the amount of cookies brought to the store as "x" kg.

On the first day, 52 kg of cookies were sold. On the second day, the amount sold was 1.3 times less than on the first day.

The amount sold on the second day = 52 kg - (1.3 * 52 kg) = 52 kg - 67.6 kg = -15.6 kg (negative because it is less than zero)

Since the amount sold on the second day cannot be negative, we need to adjust our approach.

Let's assume the amount sold on the second day is "y" kg. Therefore, the amount brought to the store would be the sum of the amount sold on the first and second days.

x = 52 kg + y kg

We also know that the total amount sold in two days is 1/3 of the amount brought to the store:

52 kg + y kg = (1/3) * x

To solve this equation, we need to eliminate the variable "y". We can substitute the value of x from the first equation into the second equation:

52 kg + y kg = (1/3) * (52 kg + y kg)

Multiplying both sides by 3 to eliminate the fraction:

3 * (52 kg + y kg) = 52 kg + y kg

156 kg + 3y kg = 52 kg + y kg

Combining like terms:

2y kg = -104 kg

Dividing both sides by 2:

y kg = -52 kg

Since the amount sold on the second day cannot be negative, we need to re-evaluate our approach. It seems there is an error or inconsistency in the given information. Please double-check the details of the problem or provide additional information if available.