Question

Сережа и Боря вскапывают грядку вместе за 12 минут, а один Сережа за 20 минут. За сколько минут грядку вскопает один Боря?

Answer 1

Все на фото...............

Answer 2

To solve this problem, let's first find the individual rates of work for both Serega and Borya.

Let's assume that the amount of work to be done (vskapывание грядки) is considered as 1 unit.

Serega's work rate (per minute) = 1/20 (because Serega takes 20 minutes to complete 1 unit of work)

Together, Serega and Borya complete 1 unit of work in 12 minutes.

Their combined work rate (per minute) = 1/12

Now, to find Borya's work rate, we'll subtract Serega's work rate from the combined work rate:

Borya's work rate (per minute) = Combined work rate - Serega's work rate Borya's work rate (per minute) = 1/12 - 1/20 Borya's work rate (per minute) = (20 - 12) / (12 * 20) Borya's work rate (per minute) = 8 / 240 Borya's work rate (per minute) = 1/30

Now, we have Borya's work rate, which is 1/30 units per minute. To find out how long it takes Borya to complete 1 unit of work (vskapывание грядки) alone, we take the reciprocal of his work rate:

Time taken by Borya (in minutes) = 1 / Borya's work rate Time taken by Borya (in minutes) = 1 / (1/30) Time taken by Borya (in minutes) = 30 minutes

So, it will take Borya 30 minutes to complete the work of vskapывание грядки alone.