1. After treating the garden with a caterpillar control agent, the gardener noticed that from 12 blackcurrant bushes he was getting the same harvest as before from 15 bushes. By what percentage did the blackcurrant yield in the garden increase?
Answer: $25 \%$.

Solution. The yield from 12 bushes increased by $15 / 12=1.25$ times, which means the yield of currants increased by $25 \%$.