For the renovation of the apartment, we bought 8 rolls of wallpaper 10m and 50cm long after the renovation

For the renovation of the apartment, we bought 8 rolls of wallpaper 10m and 50cm long after the renovation, one fourth of the purchased wallpaper remained, how many meters of wallpaper remained.

To calculate how many meters of wallpaper are left after the renovation, if it is said that in total we bought 8 rolls of wallpaper 10 meters long and 50 centimeters long, and after the renovation, one fourth of the wallpaper remained.
So we first need to calculate how many meters were purchased wallpaper.
To do this, we need the number of rolls, multiply by the number of meters in a roll, but before that convert the size to centimeters, and after calculating the result, divide by 4.
10 * 100 = 1000;
1000 + 50 = 1050;
1050 * 8 = 8400;
8400: 4 = 2100;
2100: 100 = 21.
After the renovation, 21 meters of wallpaper remained.