Coin Stacks II

It is possible to mix coins in a stack to get a stack a whole number of millimeters high. For example, a stack of 2 nickels and 2 pennies has a height of exactly 2 × 1.95 + 2 × 1.55 = 7 mm. Can you find a stack of coins with a whole number of millimeters less than 7?

Russian Mathematicians Again

"Well," said Pavel. "I have two sons closer to one another in age than your two girls, though still some years apart. It is, perhaps, a coincidence that the product of their ages is exactly six times the sum."
"Ah," said Grigori. "Thank you for letting me know their ages."
How old are Pavel's sons?

Russian Mathematicians

Two Russian mathematicians, Pavel and Grigori met at a conference in Vienna where the following conversation ensued:
Pavel: Grigori! It's been such a long time. How are you?
Grigori: Fine, Pavel. And you? I hope you are well.
Pavel: Indeed, I am. It must be fifteen years. You have children now, I believe.
Grigori: Yes two darling girls.
Pavel: And how old are they?
Grigori: Well, it's curious. The product of their ages this year is just three times the sum.
Pavel: I'm sorry, Grigori, but I still can't work out their ages.
Grigori: Of course. I forgot to tell you how excited little Nikki was when Pavla was born.
Pavel then knew the ages of the two girls. What are they? How old was Nikki when Pavla was born?