19. A wheel has a diameter of 80 cm Calculate its circumference and then find how many cómplètế turns it must have made in moving forwards 100 metres.

【Step 1】: Proceed to calculate wheel circumferenceThe first thing we need to understand is how to calculate the circumference of a wheel. For this purpose, the formula used should be of circumference of a circle, powered by the diameter of the respective circle.Although the diameter is given in centimetres(cm), you'll need to convert this into meters to keep things consistent. So, initially convert 80 cm into meters by dividing by 100 (since 1m = 100cm), giving us 0.8m.The formula for the circumference (C) in terms of diameter (d) is: C = πd So we substitute our given diameter (0.8m) into this formula: C = π * 0.8 = 2.512Where π (Pi) is approximately 3.14, a fundamental constant in mathematics. The resulting circumference is then about 2.51 meters (rounded to the nearest hundredths place).【Step 2】: Determine number of wheel turnsThe next thing we need to calculate is the number of complete wheel rotations required for the wheel to move forward a given distance (100m in this case). Hence, if each rotation of the wheel covers a distance equal to the circumference of the wheel, we can find the number of turns by dividing the total distance by the wheel’s circumference. Let's denote T as the number of turns: T = Total distance / Wheel circumferenceSubstituting our known values for the distance (100m) and the circumference (2.51m): T = 100 / 2.51 = 39.84 Scrolling up to two decimal places to obtain a more precise picture of advance motion, it is estimated that wheel requires approximately 39.84 rotations.【Answer】: A wheel with a diameter of 80 cm has approximately a 2.51 meters long circumference, and will make around 40 (Slightly less: 39.84) full rotations to cover a total 100 meter distance.