Question

Первая бригада может выполнить ремонт школы за 28 дней , а вторая за 21 день .За сколько дней сделают ремонт две бригады если будут работать вместе.

Answer 1

28-21=7
7*2=14 дней это две бригады сделают ремонт

Answer 2

Calculation of Repair Time for Two Brigades

To determine how long it will take for two brigades to complete the school repairs when working together, we need to calculate the combined efficiency of both brigades.

The first brigade can complete the repair in 28 days, while the second brigade can complete it in 21 days. To find the combined efficiency, we can calculate the harmonic mean of the individual completion times.

The harmonic mean is calculated as follows:

Harmonic Mean = 2 / ((1 / Time1) + (1 / Time2))

Substituting the given values:

Harmonic Mean = 2 / ((1 / 28) + (1 / 21))

Calculating the harmonic mean:

Harmonic Mean = 2 / (0.0357 + 0.0476) = 2 / 0.0833 ≈ 24

Therefore, when the two brigades work together, they will be able to complete the repair in approximately 24 days.