The problem-solving of the math big ability competition is as follows:

The first, first and second prizes account for 2/5 of the total, and the second and third prizes account for 9/10 of the total; The sum of the two comparisons plus and minus 1 is equal to the proportion of the second prize;

The calculation formula of the second and second prizes is as follows:

2/5+9/ 10- 1

=4/ 10+9/ 10- 1

= 13/ 10- 1

=3/ 10

Three, the calculation formula of the first prize is as follows:

2/5-3/ 10

=4/ 10-3/ 10

= 1/ 10

The calculation method of the fourth prize and the third prize is as follows:

9/ 10-3/ 10=6/ 10=3/5