Question

Строители возводили дачный домик 9 дней.Но жуткий ураган разрушил этот дом.Пришлось строить заново.Чтобы дело спорилось быстрее,решили позвать ещё 4 строителей.На этот раз построили за 3 дня.Сколько строителей было в первом случае?- а) 3,б) 1,в) 2,г) 5,д)4

Answer 1

х - число строителей в первый раз. Составим уравнение:
х*9 = (х+4)*3
9х = 3х + 12
6х = 12
х = 2

Answer 2

Question Analysis

The question is asking how many builders were there in the first case when it took 9 days to build the house, and then 4 additional builders were called in to rebuild it in 3 days.

Answer

To determine the number of builders in the first case, we can compare the time it took to build the house in both cases. In the first case, it took 9 days to build the house, while in the second case, with the additional 4 builders, it took only 3 days. Therefore, the number of builders in the first case must have been 5 (г), since the addition of 4 more builders reduced the construction time by 6 days.

Explanation

The question states that it took 9 days to build the house in the first case. Then, due to the destruction caused by a hurricane, the house had to be rebuilt. To speed up the process, 4 additional builders were called in, and this time it took only 3 days to build the house.

Since the addition of 4 more builders reduced the construction time by 6 days, it can be inferred that the original number of builders must have been 5. This is because if it took 9 days with the original number of builders, and then it took 3 days with the addition of 4 more builders, the total reduction in time is 6 days. Therefore, the original number of builders must have been 5.