A math problem about probability in grade two.

Solution: (1) If you touch the ball:

The probability of obtaining 500 yuan shopping vouchers is: p(500)= 1

The probability of obtaining 300 yuan shopping vouchers is: p(300)= 1

The probability of obtaining 5 yuan shopping vouchers is: p(5)= 1

Then the average amount of a shopping voucher that can be obtained at one touch is:

(yuan),

If 5000 people take part in touching the ball, the amount paid by the mall is:

(yuan);

(2) If the shopping voucher is directly obtained, the amount paid by the mall is:

(yuan),

By comparing the above two schemes, it is cost-effective for shopping malls to choose the promotion scheme of playing the edge ball.