Question

Группа из 5 тракторов вспахала первое поле за 14 дней. Площадь второго поля на 80% больше первого. Сколько тракторов нужно, чтобы вспахать второе поле за 18 дней?​

Answer 1

Пошаговое объяснение:

80%=80/100=0,8

Пусть первое поле 1 ч

Пропорция :

5 трак - 14 дней

1 трак - х дней

5/1=х/14

Х=5×14=70 дней нужно 1 трактору вспахать первое поле.

1+0,8=1,8 ч второе поле

Пропорция :

1ч - 70 дней

1,8 ч - х дней

Х=1,8×70:1=126 дней нужно 1 трактору вспахать второе поле.

Пропорция :

1 трак - 126 дней

Х трак - 18 дней

1/х=18/126

Х=126/18=7 тракторов нужно, чтобы вспахать второе поле за 18 дней

Ответ : 7 тракторов

Answer 2

Problem Analysis

We are given that a group of 5 tractors plowed the first field in 14 days. The area of the second field is 80% larger than the first field. We need to determine how many tractors are needed to plow the second field in 18 days.

Solution

To solve this problem, we can use the concept of work rate. The work rate is the amount of work done per unit of time. In this case, the work is plowing the field, and the unit of time is a day.

Let's assume that the work rate of the group of 5 tractors is 1 unit of work per day. This means that the group of 5 tractors can plow the first field in 14 days.

Since the area of the second field is 80% larger than the first field, we can calculate the work required to plow the second field as follows:

Work required for the second field = Work required for the first field + 80% of the work required for the first field

Let's denote the work required for the first field as W. The work required for the second field can be expressed as:

Work required for the second field = W + 0.8W = 1.8W

Now, we need to determine how many tractors are needed to plow the second field in 18 days. Let's denote the number of tractors needed as N.

The work rate of N tractors is N times the work rate of 1 tractor. Therefore, the work rate of N tractors is N units of work per day.

We can set up a proportion to solve for N:

5 tractors / 14 days = N tractors / 18 days

Cross-multiplying, we get:

5 * 18 = 14 * N

Simplifying, we find:

90 = 14N

Dividing both sides by 14, we get:

N = 90 / 14 ≈ 6.43

Since we cannot have a fraction of a tractor, we round up to the nearest whole number. Therefore, we need 7 tractors to plow the second field in 18 days.

Answer

To plow the second field in 18 days, approximately 7 tractors are needed.