Number of events =(75-25)÷2+ 1=26 ... How many rows of seats are there?

25+27+29+3 1+......+75

=(25+75)×26÷2

= 100×26÷2

=2600÷2

= 1300

Tell children the story of Gauss.

Gauss's most famous story is that when he was ten years old, the primary school teacher gave an arithmetic problem: "Calculate 1+2+3 …+ 100 =?" . This is difficult for beginners of arithmetic, but Gauss solved the answer in a few seconds. He used the symmetry of arithmetic progression (arithmetic progression) and then put the numbers together like a general arithmetic progression sum: 1+ 100, 2+99, 3+98, ... 49+52.