QUESTIONS

Q: In the recent film Gifted, one of the main characters uses the Trachtenberg system of calculating mathematical problems. Is this a real system and, if so, how does it work and who developed it?

Adeyemi Banjo, London SE15.

Q: Why did the Victorians troll each other with hate-mail known as vinegar valentines?

Leslie Parker, Nuneaton, Warks.

Q: Where was the world’s first working nuclear power station?

Mary Ames, Poole, Dorset.