Practice — 45 people can finish a project in 15 days. For the same workload, 15 people are used. All people have equal productivity. In how many days can this project be completed?

Tuna idadi ya awali ya watu ($P_1$) na siku ($D_1$), na idadi mpya ya watu ($P_2$). Tunahitaji kupata idadi mpya ya siku ($D_2$).
$P_1 = 45$ watu
$D_1 = 15$ siku
$P_2 = 15$ watu
$D_2 = ?$ siku

Kwa uwiano usio wa moja kwa moja, bidhaa ya idadi ya watu na siku inabaki sawa:

Kwanza, zidisha upande wa kushoto:

Sasa, gawanya pande zote mbili kwa 15 ili kupata $D_2$:

Hivyo, mradi utakamilika kwa siku 45.

Jibu sahihi ni 45 days.
$\text{45 days}$