A Fit Sports Goods Store in a certain city made statistics on the sales of a certain brand of men's running shoes for a week, and plotted the statistical data into the unfinished chart below.

Solution: (1) ∵The frequency of shoes No. 39 is 10, the frequency of shoes No. 42 is 5 greater than the frequency of running shoes No. 39,

∴The frequency of shoes No. 42 is; 15=15,

∵The frequency of running shoes No. 42 is 0.15,

∴The total number of men’s running shoes of this brand sold this week is: 15÷0.15=100 (pairs),< /p>

Answer: ***100 pairs of men’s running shoes of this brand are sold in a week.

(2) ∵The total number of shoes is 100, there are 10 pairs of size 39, 15 pairs of size 40, 15 pairs of size 43, 5 pairs of size 44, and 15 pairs of size 42 Double,

The size ∴41 is: 100-10-15-15-5-15=40 (double),

The supplementary picture is as follows:

(3) According to the question:

5100×1000=50 (pairs),

Answer: It is estimated that 50 pairs of size 44 running shoes will be needed.