16 added to the sum of the first few terms of the arithmetic sequence 9, 11, 13, … gave 256. How many terms were added?

An isosceles triangle has to be made like this

The height should be 2 metres less than the base. What should be the length of its sides?

A 2.6 metres long rod leans against a wall, its foot 1 metre from the wall. When the foot is moved a little away from the wall, its upper end slides the same length down. How much farther is the foot moved?

How many terms of the arithmetic sequence 5, 7, 9, …, must be added to get 140?

A mathematician travelled three hundred kilometres to attend a conference. During his take he said: “Had my average speed been increased by 10 kilometres per hour, I could have reached here one hour earlier.” What was the average speed?