Petya's mother also gave him money for pencils. The conditions of the promotional offer are the same as in problem 104109). Petya tried to buy as many pencils as possible and as a result, he was able to buy 12 more pencils than his mother asked for. How many pencils did his mother give money for?
By repeating the reasoning of problem 104109, we can be convinced that if Mom gave Petya money for 49 pencils, then he could buy 61 pencils, which is 12 more pencils than Mom asked for. Therefore, 49 is one of the answers. Similarly, we can check that if Mom had given Petya money for 50 pencils, then he could have bought 66 pencils, which is 16 more pencils than Mom asked for. And if Mom had given Petya money for 48 pencils, then he could have bought 59 pencils, which is only 11 more pencils than Mom asked for. Clearly, the more money Mom gives Petya, the more he can gain from the promotion. Therefore, Mom could not have given him more or less money than for 49 pencils, which means 49 is the only answer.

## Answer

For 49 pencils.