Brain Teasers and Puzzles 

Workings

Hint
The word starts with B.

Answer
Border becomes boarder.

Workings

Hint
The country spans more than one word.

Answer
Chile.

At school, most of my friends learnt FrenCH. I LEarnt Chinese, mainly because I planned to visit the area when I grew up.

Workings

Hint
Some are much more common than others.

Answers
Common: vacuum, vacuumed, vacuuming, vacuums.

Less common: continuum, continuums, muumuu, muumuus.

Much less common: carduus, carduuses, continuua, duumvir, duumviral, duumvirate, duumvirates, duumviri, duumvirs, individuum, individuums, lituus, lituuses, menstruum, menstruums, mutuum, mutuums, paramenstruum, paramenstruums, residuum, residuums, squush, squushed, squushes, squushier, squushiest, squushing, squushy, triduum, triduums, ultravacuum, ultravacuums, weltanschauung, weltanschauungen, weltanschauungs.

Workings

Hint
The first word ends in k.

Answer
Look before you leap.