If 5 spiders can catch five flies in five minutes. How many flies can hundred spiders catch in 100 minutes?

The rate at which spiders catch the flies remains the same. Hence multiplying the time frame and the number of spiders relative to the information provided gives the solution.

Distributing 5 spiders as a group. There are 20 groups and each group catches 5 spiders in 5 minutes ad hence 100 spiders are caught in 5 minutes and in 100 minutes.

100*(100)/5 = 2000 flies.

$$\frac{\left(M1\cdot D1\cdot\right)}{W1}\ =\frac{\left(M2\cdot D2\right)}{W2}$$

$$\frac{\left(5\cdot5\right)}{5}\ =\frac{\left(100\cdot100\right)}{W2}$$

=> W= 2000