Hint: Say what you see.

Answer: Square dance.

Hint: How much petrol did I use driving?

Answer: 3 gallons per hour.

I drove 300 miles at 30 miles per gallon, so I used 10 gallons. Which means I lost the other 15 gallons.

I drove the 300 miles at 60mph, which took me 5 hours.

So I lost 15 gallons of petrol in 5 hours = 3 gallons per hour.

Hint: Not so much a test, more of a ==?==

Answer: Challenge.

Hint: Hopefully you won't need one for a very long time.

Answer: A coffin.

Hint: Every word must contain the central letter.

Answer: Passenger.

Common words:
   age, agree, anger, eager, enrage, gap, gape, gas, gasp, gasper, gasser, gear, gee, gene, genre, grape, grasp, grass, grease, green, nag, page, pager, pang, PASSENGER, peg, rag, rage, rang, range, sag, sage, sang, snag, sprang.

All words:
   ag, age, agee, agene, agenes, ager, agers, ages, agree, agrees, anger, angers, asperges, eager, eagers, eagre, eagres, eger, egers, egress, eng, engs, enrage, enrages, erg, ergs, gae, gaen, gaes, gan, gane, gap, gape, gaper, gapers, gapes, gaps, gar, gars, gas, gases, gasp, gasper, gaspers, gasps, gasser, gear, gears, gee, gees, gen, gene, genera, genes, genre, genres, gens, gnar, gnars, gran, grans, grape, grapes, grasp, grasps, grass, grease, greases, gree, green, greens, grees, nag, nags, page, pager, pagers, pages, pang, pangs, parge, parges, PASSENGER, peag, peage, peages, peags, peg, pegs, prang, prangs, presage, presages, rag, rage, ragee, ragees, rages, rags, rang, range, ranges, reg, reges, regna, regs, repeg, repegs, sag, sage, sager, sages, sags, sang, sanger, sangers, sarge, sarges, seg, segs, senega, senegas, serge, serges, snag, snags, spang, sparge, sparges, sprag, sprags, sprang, sprangs.