Question

Три эксковатора различной мощности могут вырыть котлован работая по отлельности : первый - за 10 д второй - за 12 д третий -за 15 д за сколько времени они выроют котлован вместе?

Answer 1

Вроде так но это не точно 
Первый в день делает 1/10 работы.Второй - 1/12 работы.
Третий - 1/15 работы.
Вместе они будут в день делать от всей работы 1/10+1/12+1/15 = 6/60+5/60+4/60=15/60=1/4.В день три экскаватора делают вместе 1/4 часть работы. Всю работу выполнят за 1:1/4=4дня.

Answer 2

Calculating Excavation Time for Three Excavators

To calculate the time it takes for three excavators of different power to dig a pit together, we can use the concept of their combined work rate.

Let's denote the work rate of the first excavator as W1, the work rate of the second excavator as W2, and the work rate of the third excavator as W3.

The work rate of each excavator can be calculated as the reciprocal of the time it takes for each excavator to dig the pit individually.

- Work rate of the first excavator, W1 = 1/10 (as it can dig the pit in 10 days) - Work rate of the second excavator, W2 = 1/12 (as it can dig the pit in 12 days) - Work rate of the third excavator, W3 = 1/15 (as it can dig the pit in 15 days)

To find the combined work rate of all three excavators working together, we simply add their individual work rates:

Combined work rate = W1 + W2 + W3

Now, we can calculate the time it takes for all three excavators to dig the pit together using the combined work rate.

Let's proceed with the calculation.