Percentages

In an e-sports tournament, $20\%$ of the $150$ participants play on a tablet, while the rest play on a computer. Calculate the exact number of players using a tablet to compete.

Work out the following percentages mentally using the division strategies learned in class (divide by $2$ for $50\%$, by $4$ for $25\%$ and by $10$ for $10\%$):

1. a) $50\%$ of $84$ viewers on a livestream.
2. b) $25\%$ of a $400$ gram pizza.
3. c) $10\%$ of a travel pass costing $35$ euros.

The loading bar of your favourite video game shows that $75\%$ of the total download has been completed. If the full file takes up $40$ GB, how many gigabytes have been downloaded so far?

The battery of Lucía's tablet has a total capacity of $5000$ mAh. If after playing "Roblox" for a while she has $18\%$ battery left, how many mAh of power does she still have? What percentage of the battery has she already used?

In a trendy shoe shop, a pair of trainers costing $85 \text{ €}$ has a discount of $20\%$. However, as it is the last day of the sale, an additional discount of $10\%$ is applied to the already reduced price. What is the final price of the trainers? Is it the same as applying a single discount of $30\%$? Justify your answer by calculating both cases.

An adventure video game takes up $12$ GB in a console's memory. If the system indicates that this game takes up $15\%$ of the total available memory, how many GB of capacity does the console's memory have in total?

Álex bought a computer to play his favourite video games. The final price he paid, including $21\%$ VAT, was $1452 \text{ €}$. His friend tells him that the computer cost $1200 \text{ €}$ before taxes. Is his friend right? Perform the necessary calculations to find the base price (excluding VAT) of the computer.

The storage of a mobile phone is $128 \text{ GB}$. The operating system takes up $12,5\%$ of the total. If Álex has already used up $60\%$ of the remaining free space, how many gigabytes does he still have available to install new apps?