The mosquito flaps its wings at a frequency of 700 Hz (i.e. makes 700 flaps per second).

The mosquito flaps its wings at a frequency of 700 Hz (i.e. makes 700 flaps per second). The mosquito’s flight speed is 2 km / h. Estimate, in order of magnitude, how many swings a mosquito has to make to fly 1 km.

The mosquito’s flight speed is 2 km / h, which means that it will fly 1 km in 1: 2 = 0.5 hours = 30 minutes.
30 minutes = 1800 seconds = 1.8 * 10³ seconds.
During this time, the mosquito will:
700 * 1.8 * 10³ = 7 * 1.8 * 10³ * 10² = 7 * 1.8 * 10⁵ flaps of the wings.
Thus, the number of flaps of the wings will be of the fifth order.